Case-insensitive search

Question

I m trying to get a case-insensitive search with two strings in JavaScript working   Normally it would be like this   var string  Stackoverflow is the BEST   var result  string search  best i   alert result     The  i flag would be for case-insensitive   But I need to search for a second string  without the flag it works perfect   var string  Stackoverflow is the BEST   var searchstring  best   var result  string search searchstring   alert result     If I add the  i flag to the above example it would search for searchstring and not for what is in the variable  searchstring   next example not working    var string  Stackoverflow is the BEST   var searchstring  best   var result  string search  searchstring i   alert result     How can I achieve this

User · Answer

ES6    let string  Stackoverflow is the BEST   let searchstring  best     let found   string toLowerCase                      includes searchstring toLowerCase       includes   returns true if searchString appears at one or more positions or false otherwise

User · Answer

I like  CHR15TO s answer  unlike other answers I ve seen on other similar questions  that answer actually shows how to properly escape a user provided search string  rather than saying it would be necessary without showing how    However  it s still quite clunky  and possibly relatively slower  So why not have a specific solution to what is likely a common requirement for coders   And why not include it in the ES6 API BTW    My answer  https   stackoverflow com a 38290557 887092  on a similar question enables the following   var haystack    A  BAIL  Of  Hay    var needle    bail    var index   haystack naturalIndexOf needle

User · Answer

Replace  var result  string search  searchstring i     with  var result  string search new RegExp searchstring   i

User · Answer

If you re just searching for a string rather than a more complicated regular expression  you can use indexOf   - but remember to lowercase both strings first because indexOf   is case sensitive   var string  Stackoverflow is the BEST    var searchstring  best       lowercase both strings var lcString string toLowerCase    var lcSearchString searchstring toLowerCase     var result   lcString indexOf lcSearchString  gt  0  alert result     Or in a single line   var result   string toLowerCase   indexOf searchstring toLowerCase    gt  0

User · Answer

If you are concerned about the  unterminated character class  case  removing all non-alphanumeric chars would be helpful   searchstring   searchstring replace    a-zA-Z 0-9   g

User · Answer

Yeah  use  match  rather than  search  The result from the  match call will return the actual string that was matched itself  but it can still be used as a boolean value   var string    Stackoverflow is the BEST   var result   string match  best i      result     BEST    if  result       alert  Matched        Using a regular expression like that is probably the tidiest and most obvious way to do that in JavaScript  but bear in mind it is a regular expression  and thus can contain regex metacharacters  If you want to take the string from elsewhere  eg  user input   or if you want to avoid having to escape a lot of metacharacters  then you re probably best using indexOf like this   matchString    best      If the match string is coming from user input you could do    matchString   userInput toLowerCase   here   if  string toLowerCase   indexOf matchString     -1       alert  Matched

User · Answer

Replace  var result  string search  searchstring i     with  var result  string search new RegExp searchstring   i

User · Answer

If you re just searching for a string rather than a more complicated regular expression  you can use indexOf   - but remember to lowercase both strings first because indexOf   is case sensitive   var string  Stackoverflow is the BEST    var searchstring  best       lowercase both strings var lcString string toLowerCase    var lcSearchString searchstring toLowerCase     var result   lcString indexOf lcSearchString  gt  0  alert result     Or in a single line   var result   string toLowerCase   indexOf searchstring toLowerCase    gt  0

User · Answer

There are two ways for case insensitive comparison    Convert strings to upper case and then compare them using the strict operator        How strict operator treats operands read stuff at  http   www thesstech com javascript relational-logical-operators Pattern matching using string methods   Use the  search  string method for case insensitive search  Read about search and other string methods at  http   www thesstech com pattern-matching-using-string-methods    lt  doctype html gt     lt html gt       lt head gt         lt script gt              1st way          var a    apple           var b    APPLE             if  a toUpperCase       b toUpperCase                alert  equal                         2nd way          var a     Null and void           document write a search  null i             lt  script gt       lt  head gt   lt  html gt

User · Answer

If you are concerned about the  unterminated character class  case  removing all non-alphanumeric chars would be helpful   searchstring   searchstring replace    a-zA-Z 0-9   g

User · Answer

I do this often and use a simple 5 line prototype that accepts varargs   It is fast and works everywhere   myString containsIgnoreCase  red   orange   yellow      x000D   x000D      x000D      param     string  var strings Strings to search for x000D      return  boolean  true if ANY of the arguments is contained in the string x000D      x000D  String prototype containsIgnoreCase   function var strings    x000D    const thisLowerCase   this toLowerCase   x000D    for  let i   0  i  lt  arguments length  i      x000D      let needle   arguments i  x000D      if  thisLowerCase indexOf needle toLowerCase     gt   0    x000D        return true x000D        x000D      x000D    return false x000D    x000D   x000D      x000D      param     string  var strings Strings to search for x000D      return  boolean  true if ALL of the arguments are contained in the string x000D      x000D  String prototype containsAllIgnoreCase   function var strings    x000D    const thisLowerCase   this toLowerCase   x000D    for  let i   0  i  lt  arguments length  i      x000D      let needle   arguments i  x000D      if  thisLowerCase indexOf needle toLowerCase        -1    x000D        return false x000D        x000D      x000D    return true x000D    x000D   x000D     Unit test x000D   x000D  let content     x000D  FIRST SECOND x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D  FOO BAR x000D    x000D   x000D  let data     x000D     foo   x000D     Foo   x000D     foobar   x000D     barfoo   x000D     first   x000D     second  x000D    x000D   x000D  let result x000D  data forEach item   gt    x000D    console log  Searching for   item  x000D    result   content containsIgnoreCase item  x000D    console log result    Found     Not Found   x000D     x000D   x000D  console log  Searching for    x  y  foo   x000D  result   content containsIgnoreCase  x    y    foo    x000D  console log result    Found     Not Found   x000D   x000D  console log  Searching for all    foo  bar  foobar   x000D  result   content containsAllIgnoreCase  foo    bar    foobar    x000D  console log result    Found     Not Found   x000D   x000D  console log  Searching for all    foo  bar   x000D  result   content containsAllIgnoreCase  foo    bar    x000D  console log result    Found     Not Found   x000D   x000D   x000D

User · Answer

Yeah  use  match  rather than  search  The result from the  match call will return the actual string that was matched itself  but it can still be used as a boolean value   var string    Stackoverflow is the BEST   var result   string match  best i      result     BEST    if  result       alert  Matched        Using a regular expression like that is probably the tidiest and most obvious way to do that in JavaScript  but bear in mind it is a regular expression  and thus can contain regex metacharacters  If you want to take the string from elsewhere  eg  user input   or if you want to avoid having to escape a lot of metacharacters  then you re probably best using indexOf like this   matchString    best      If the match string is coming from user input you could do    matchString   userInput toLowerCase   here   if  string toLowerCase   indexOf matchString     -1       alert  Matched

User · Answer

I like  CHR15TO s answer  unlike other answers I ve seen on other similar questions  that answer actually shows how to properly escape a user provided search string  rather than saying it would be necessary without showing how    However  it s still quite clunky  and possibly relatively slower  So why not have a specific solution to what is likely a common requirement for coders   And why not include it in the ES6 API BTW    My answer  https   stackoverflow com a 38290557 887092  on a similar question enables the following   var haystack    A  BAIL  Of  Hay    var needle    bail    var index   haystack naturalIndexOf needle

User · Answer

I noticed that if the user enters a string of text but leaves the input without selecting any of the autocomplete options no value is set in the hidden input  even if the string coincides with one in the array  So  with help of the other answers I made this   var  local source              value  1          label   c                     value  2          label   java                   value  3          label   php                   value  4          label   coldfusion                   value  5          label   javascript                   value  6          label   asp                   value  7          label   ruby                  search-fld   autocomplete           source   local source          select  function  event  ui                    search-fld   val ui item label      display the selected text                 search-fldID   val ui item value      save selected id to hidden input             return false                     change  function  event  ui                  var isInArray   false                local source forEach function element  index                    if      search-fld   val   toUpperCase      element label toUpperCase                          isInArray   true                          search-fld   val element label      display the selected text                         search-fldID   val element value      save selected id to hidden input                     console log  inarray    isInArray   label    element label   value    element value                                                    if  isInArray                        search-fld   val         display the selected text                      search-fldID    val  ui item  ui item value   0

User · Answer

Replace  var result  string search  searchstring i     with  var result  string search new RegExp searchstring   i

User · Answer

Yeah  use  match  rather than  search  The result from the  match call will return the actual string that was matched itself  but it can still be used as a boolean value   var string    Stackoverflow is the BEST   var result   string match  best i      result     BEST    if  result       alert  Matched        Using a regular expression like that is probably the tidiest and most obvious way to do that in JavaScript  but bear in mind it is a regular expression  and thus can contain regex metacharacters  If you want to take the string from elsewhere  eg  user input   or if you want to avoid having to escape a lot of metacharacters  then you re probably best using indexOf like this   matchString    best      If the match string is coming from user input you could do    matchString   userInput toLowerCase   here   if  string toLowerCase   indexOf matchString     -1       alert  Matched

User · Answer

I noticed that if the user enters a string of text but leaves the input without selecting any of the autocomplete options no value is set in the hidden input  even if the string coincides with one in the array  So  with help of the other answers I made this   var  local source              value  1          label   c                     value  2          label   java                   value  3          label   php                   value  4          label   coldfusion                   value  5          label   javascript                   value  6          label   asp                   value  7          label   ruby                  search-fld   autocomplete           source   local source          select  function  event  ui                    search-fld   val ui item label      display the selected text                 search-fldID   val ui item value      save selected id to hidden input             return false                     change  function  event  ui                  var isInArray   false                local source forEach function element  index                    if      search-fld   val   toUpperCase      element label toUpperCase                          isInArray   true                          search-fld   val element label      display the selected text                         search-fldID   val element value      save selected id to hidden input                     console log  inarray    isInArray   label    element label   value    element value                                                    if  isInArray                        search-fld   val         display the selected text                      search-fldID    val  ui item  ui item value   0

User · Answer

There are two ways for case insensitive comparison    Convert strings to upper case and then compare them using the strict operator        How strict operator treats operands read stuff at  http   www thesstech com javascript relational-logical-operators Pattern matching using string methods   Use the  search  string method for case insensitive search  Read about search and other string methods at  http   www thesstech com pattern-matching-using-string-methods    lt  doctype html gt     lt html gt       lt head gt         lt script gt              1st way          var a    apple           var b    APPLE             if  a toUpperCase       b toUpperCase                alert  equal                         2nd way          var a     Null and void           document write a search  null i             lt  script gt       lt  head gt   lt  html gt

User · Answer

You can make everything lowercase   var string  Stackoverflow is the BEST   var searchstring  best   var result   string toLowerCase    search  searchstring toLowerCase      alert result

User · Answer

You can make everything lowercase   var string  Stackoverflow is the BEST   var searchstring  best   var result   string toLowerCase    search  searchstring toLowerCase      alert result

User · Answer

Replace  var result  string search  searchstring i     with  var result  string search new RegExp searchstring   i

User · Answer

I do this often and use a simple 5 line prototype that accepts varargs   It is fast and works everywhere   myString containsIgnoreCase  red   orange   yellow      x000D   x000D      x000D      param     string  var strings Strings to search for x000D      return  boolean  true if ANY of the arguments is contained in the string x000D      x000D  String prototype containsIgnoreCase   function var strings    x000D    const thisLowerCase   this toLowerCase   x000D    for  let i   0  i  lt  arguments length  i      x000D      let needle   arguments i  x000D      if  thisLowerCase indexOf needle toLowerCase     gt   0    x000D        return true x000D        x000D      x000D    return false x000D    x000D   x000D      x000D      param     string  var strings Strings to search for x000D      return  boolean  true if ALL of the arguments are contained in the string x000D      x000D  String prototype containsAllIgnoreCase   function var strings    x000D    const thisLowerCase   this toLowerCase   x000D    for  let i   0  i  lt  arguments length  i      x000D      let needle   arguments i  x000D      if  thisLowerCase indexOf needle toLowerCase        -1    x000D        return false x000D        x000D      x000D    return true x000D    x000D   x000D     Unit test x000D   x000D  let content     x000D  FIRST SECOND x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D   At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident  similique sunt in culpa qui officia deserunt mollitia animi  id est laborum et dolorum fuga  Et harum quidem rerum facilis est et expedita distinctio  Nam libero tempore  cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus  omnis voluptas assumenda est  omnis dolor repellendus  Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae  Itaque earum rerum hic tenetur a sapiente delectus  ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat   x000D  FOO BAR x000D    x000D   x000D  let data     x000D     foo   x000D     Foo   x000D     foobar   x000D     barfoo   x000D     first   x000D     second  x000D    x000D   x000D  let result x000D  data forEach item   gt    x000D    console log  Searching for   item  x000D    result   content containsIgnoreCase item  x000D    console log result    Found     Not Found   x000D     x000D   x000D  console log  Searching for    x  y  foo   x000D  result   content containsIgnoreCase  x    y    foo    x000D  console log result    Found     Not Found   x000D   x000D  console log  Searching for all    foo  bar  foobar   x000D  result   content containsAllIgnoreCase  foo    bar    foobar    x000D  console log result    Found     Not Found   x000D   x000D  console log  Searching for all    foo  bar   x000D  result   content containsAllIgnoreCase  foo    bar    x000D  console log result    Found     Not Found   x000D   x000D   x000D

User · Answer

Yeah  use  match  rather than  search  The result from the  match call will return the actual string that was matched itself  but it can still be used as a boolean value   var string    Stackoverflow is the BEST   var result   string match  best i      result     BEST    if  result       alert  Matched        Using a regular expression like that is probably the tidiest and most obvious way to do that in JavaScript  but bear in mind it is a regular expression  and thus can contain regex metacharacters  If you want to take the string from elsewhere  eg  user input   or if you want to avoid having to escape a lot of metacharacters  then you re probably best using indexOf like this   matchString    best      If the match string is coming from user input you could do    matchString   userInput toLowerCase   here   if  string toLowerCase   indexOf matchString     -1       alert  Matched

User · Answer

Suppose we want to find the string variable needle in the string variable haystack  There are three gotchas    Internationalized applications should avoid string toUpperCase and string toLowerCase  Use a regular expression which ignores case instead  For example  var needleRegExp   new RegExp needle   i    followed by needleRegExp test haystack   In general  you might not know the value of needle  Be careful that needle does not contain any regular expression special characters  Escape these using needle replace   -                   s  g       amp      In other cases  if you want to precisely match needle and haystack  just ignoring case  make sure to add     at the start and     at the end of your regular expression constructor    Taking points  1  and  2  into consideration  an example would be    var haystack    A  BAIL  Of  Hay    var needle    bail    var needleRegExp   new RegExp needle replace   -                   s  g       amp      i    var result   needleRegExp test haystack   alert result

User · Answer

If you re just searching for a string rather than a more complicated regular expression  you can use indexOf   - but remember to lowercase both strings first because indexOf   is case sensitive   var string  Stackoverflow is the BEST    var searchstring  best       lowercase both strings var lcString string toLowerCase    var lcSearchString searchstring toLowerCase     var result   lcString indexOf lcSearchString  gt  0  alert result     Or in a single line   var result   string toLowerCase   indexOf searchstring toLowerCase    gt  0

User · Answer

ES6    let string  Stackoverflow is the BEST   let searchstring  best     let found   string toLowerCase                      includes searchstring toLowerCase       includes   returns true if searchString appears at one or more positions or false otherwise

User · Answer

If you re just searching for a string rather than a more complicated regular expression  you can use indexOf   - but remember to lowercase both strings first because indexOf   is case sensitive   var string  Stackoverflow is the BEST    var searchstring  best       lowercase both strings var lcString string toLowerCase    var lcSearchString searchstring toLowerCase     var result   lcString indexOf lcSearchString  gt  0  alert result     Or in a single line   var result   string toLowerCase   indexOf searchstring toLowerCase    gt  0

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Suppose we want to find the string variable needle in the string variable haystack  There are three gotchas    Internationalized applications should avoid string toUpperCase and string toLowerCase  Use a regular expression which ignores case instead  For example  var needleRegExp   new RegExp needle   i    followed by needleRegExp test haystack   In general  you might not know the value of needle  Be careful that needle does not contain any regular expression special characters  Escape these using needle replace   -                   s  g       amp      In other cases  if you want to precisely match needle and haystack  just ignoring case  make sure to add     at the start and     at the end of your regular expression constructor    Taking points  1  and  2  into consideration  an example would be    var haystack    A  BAIL  Of  Hay    var needle    bail    var needleRegExp   new RegExp needle replace   -                   s  g       amp      i    var result   needleRegExp test haystack   alert result

[javascript] Case-insensitive search

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