Contains case insensitive

Question

I have the following   if  referrer indexOf  Ral      -1            What I like to do is to make Ral case insensitive  so that it can be RAl  rAl  etc  and still match   Is there a way to say that Ral has to be case-insensitive

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Here s my take   Script   var originalText       textContainer   html       search   on  keyup   function            textContainer   html originalText    var text       textContainer   html     var val       search   val     if val      return    var matches   text split val    for var i 0 i lt matches length-1 i          var ind    matches i  indexOf val      var len   val length       matches i    matches i      lt span class  selected  gt     val     lt  span gt             textContainer   html matches join        HTML     lt input type  text  id  search  gt   lt div id  textContainer  gt  lorem ipsum is simply dummy text of the printing and typesetting industry  lorem ipsum has been the industry s standard dummy text ever since the 1500s  when an unknown printer took a galley of type and scrambled it to make a type specimen book  It has survived not only five centuries  but also the leap into electronic typesetting  remaining essentially unchanged  It was popularised in the 1960s with the release of letraset sheets containing lorem ipsum passages  and more recently with desktop publishing software like Aldus pagemaker including versions of lorem ipsum  lt  div gt    Codepen

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There are a couple of approaches here   If you want to perform a case-insensitive check for just this instance  do something like the following   if  referrer toLowerCase   indexOf  Ral  toLowerCase       -1              Alternatively  if you re performing this check regularly  you can add a new indexOf  -like method to String  but make it case insensitive   String prototype indexOfInsensitive   function  s  b        return this toLowerCase   indexOf s toLowerCase    b         Then invoke it if  referrer indexOfInsensitive  Ral      -1

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To do a better search use the following code   var myFav      javascript   var theList    VB NET  C   PHP  Python  JavaScript  and Ruby       Check for matches with the plain vanilla indexOf   method  alert  theList indexOf  myFav          Now check for matches in lower-cased strings  alert  theList toLowerCase   indexOf  myFav toLowerCase          In the first alert    JavaScript returned  -1  - in other words  indexOf   did not find a match  this is simply because  JavaScript  is in lowercase in the first string  and properly capitalized in the second  To perform case-insensitive searches with indexOf    you can make both strings either uppercase or lowercase  This means that  as in the second alert    JavaScript will only check for the occurrence of the string you are looking for  capitalization ignored   Reference  http   freewebdesigntutorials com javaScriptTutorials jsStringObject indexOfMethod htm

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Use a RegExp   if    ral i test referrer                 Or  use  toLowerCase     if  referrer toLowerCase   indexOf  ral      -1

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Another options is to use the search method as follow   if  referrer search new RegExp  Ral    i       -1          It looks more elegant then converting the whole string to lower case and it may be more efficient   With toLowerCase   the code have two pass over the string  one pass is on the entire string to convert it to lower case and another is to look for the desired index  With RegExp the code have one pass over the string which it looks to match the desired index   Therefore  on long strings I recommend to use the RegExp version  I guess that on short strings this efficiency comes on the account of creating the RegExp object though

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Example for any language     My name is         toLocaleLowerCase   includes          toLocaleLowerCase

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You can try this   x000D   x000D  str    Wow its so COOL  x000D  searchStr    CoOl  x000D   x000D  console log str toLowerCase   includes searchStr toLowerCase     x000D   x000D   x000D

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if  referrer toUpperCase   indexOf  RAL      -1

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From ES2016 you can also use slightly better   easier   more elegant method  case-sensitive    if  referrer includes  Ral              or  case-insensitive    if  referrer toLowerCase   includes someString toLowerCase               Here is some comparison of  indexOf   and  includes    https   dev to adroitcoder includes-vs-indexof-in-javascript

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It s 2016  and there s no clear way of how to do this  I was hoping for some copypasta  I ll have a go  Design notes  I wanted to minimize memory usage  and therefore improve speed - so there is no copying mutating of strings  I assume V8  and other engines  can optimise this function    TODO  Performance testing String prototype naturalIndexOf   function needle          TODO  guard conditions here          var haystack   this    You can replace  haystack  for  this  below but I wan t to make the algorithm more readable for the answer     var needleIndex   0      var foundAt   0      for  var haystackIndex   0  haystackIndex  lt  haystack length  haystackIndex              var needleCode   needle charCodeAt needleIndex           if  needleCode  gt   65  amp  amp  needleCode  lt   90  needleCode    32    ToLower  I could have made this a function  but hopefully inline is faster and terser         var haystackCode   haystack charCodeAt haystackIndex           if  haystackCode  gt   65  amp  amp  haystackCode  lt   90  haystackCode    32    ToLower  I could have made this a function  but hopefully inline is faster and terser                    TODO  code to detect unicode characters and fallback to toLowerCase - when  gt  128            if  needleCode  gt  128    haystackCode  gt  128  return haystack toLocaleLowerCase   indexOf needle toLocaleLowerCase            if  haystackCode     needleCode                        foundAt   haystackIndex              needleIndex   0    Start again                   else             needleIndex                         if  needleIndex    needle length              return foundAt                 return -1     My reason for the name   Should have IndexOf in the name Don t add a suffix word - IndexOf refers to the following parameter  So prefix something instead  Don t use  quot caseInsensitive quot  prefix would be sooooo long  quot natural quot  is a good candidate  because default case sensitive comparisons are not natural to humans in the first place   Why not      toLowerCase   - potential repeated calls to toLowerCase on the same string  RegExp - awkward to search with variable  Even the RegExp object is awkward having to escape characters

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Add  toUpperCase   after referrer  This method turns the string into an upper case string  Then  use  indexOf   using RAL instead of Ral  if  referrer toUpperCase   indexOf  quot RAL quot       -1      The same can also be achieved using a Regular Expression  especially useful when you want to test against dynamic patterns   if    Ral i test referrer               i   Ignore case flag for RegExp

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If referrer is an array  you can use findIndex     if referrer findIndex item   gt   ral      item toLowerCase       -1

[javascript] Contains case insensitive

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