How to tell if a string contains a certain character in JavaScript

Question

I have a page with a textbox where a user is supposed to enter a 24 character  letters and numbers  case insensitive  registration code   I used maxlength to limit the user to entering 24 characters   The registration codes are typically given as groups of characters separated by dashes  but I would like for the user to enter the codes without the dashes   How can I write my JavaScript code without jQuery to check that a given string that the user inputs does not contain dashes  or better yet  only contains alphanumeric characters

User · Answer

Check if string is alphanumeric or alphanumeric   some allowed chars  The fastest alphanumeric method is likely as mentioned at  Best way to alphanumeric check in Javascript as it operates on number ranges directly   Then  to allow a few other extra chars sanely we can just put them in a Set for fast lookup   I believe that this implementation will deal with surrogate pairs correctly correctly      usr bin env node  const assert   require  assert     const char is alphanumeric   function c      let code   c codePointAt 0     return          0-9      code  gt  47  amp  amp  code  lt  58            A-Z      code  gt  64  amp  amp  code  lt  91            a-z      code  gt  96  amp  amp  code  lt  123         const is alphanumeric   function  str      for  let c of str        if   char is alphanumeric c           return false              return true         Arbitrarily defined as alphanumeric or  -  or      const is almost alphanumeric   function  str      for  let c of str        if          char is alphanumeric c   amp  amp         is almost alphanumeric almost chars has c                return false              return true     is almost alphanumeric almost chars   new Set   -           assert  is alphanumeric  aB0     assert  is alphanumeric  aB0 -     assert  is alphanumeric  aB0 -      assert  is alphanumeric          assert  is almost alphanumeric  aB0     assert  is almost alphanumeric  aB0 -     assert  is almost alphanumeric  aB0 -      assert  is almost alphanumeric           GitHub upstream   Tested in Node js v10 15 1

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To find  hello  in your string  if  your string indexOf  hello    gt  -1      alert  hello found inside your string        For the alpha numeric you can use a regular expression   http   www regular-expressions info javascript html  Alpha Numeric Regular Expression

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If you are reading data from the DOM such as a p or h1 tag  for example  you will want to use two native JavaScript functions  it is quiet easy but limited to es6  at least for the solution I am going to provide  I will search all p tags within the DOM  if the text contains a  T  the entire paragraph will be removed  I hope this little example helps someone out    HTML   lt p gt Text you need to read one lt  p gt   lt p gt Text you need to read two lt  p gt   lt p gt Text you need to read three lt  p gt    JS  let paras   document querySelectorAll  p     paras forEach p   gt      if p textContent includes  T            p remove

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If you have the text in variable foo   if       a-zA-Z0-9     test foo            Validation failed     This will test and make sure the user has entered at least one character  and has entered only alphanumeric characters

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To test for alphanumeric characters only   if     0-9A-Za-z     test yourString           there are only alphanumeric characters   else         it contains other characters     The regex is testing for 1 or more     of the set of characters 0-9  A-Z  and a-z  starting with the beginning of input     and stopping with the end of input

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x000D   x000D  var inputString    this is home   x000D  var findme    home   x000D   x000D  if   inputString indexOf findme   gt  -1     x000D      alert   found it     x000D    else   x000D      alert   not found     x000D    x000D   x000D   x000D

User · Answer

Use a regular expression to accomplish this   function isAlphanumeric  str      return    0-9a-zA-Z     test str

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If you re searching for character s  in the start or at the end of the string  you can also use startsWith and endsWith   const country    pakistan   country startsWith  p       true country endsWith  n        true

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Demonstration  The include   method finds the    contains    character in whole string  it will return a true    x000D   x000D  var string    This is a tutsmake com and this tutorial contains javascript include   method examples   x000D   x000D  str includes  contains    x000D   x000D    The output of this x000D   x000D    true x000D   x000D   x000D

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Try this   if   Hello  World   indexOf  orl       -1      alert  The string  Hello World  contains the substring  orl      else     alert  The string  Hello World  does not contain the substring  orl        Here is an example  http   jsfiddle net oliverni cb8xw

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Kevins answer is correct but it requires a  magic  number as follows   var containsChar   s indexOf somechar      -1    In that case you need to know that -1 stands for not found  I think that a bit better version would be   var containsChar   s indexOf somechar   gt   0

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Working perfectly This exmple will help alot    lt script gt          function check                var val   frm1 uname value           alert val          if  val indexOf       gt  0                     alert   email              document getElementById  isEmail1   value   true              alert  document getElementById  isEmail1   value           else             alert  usernam              document getElementById  isEmail1   value   false              alert  document getElementById  isEmail1   value                   lt  script gt    lt body gt       lt h1 gt My form  lt  h1 gt       lt form action  v1 0 user login  method  post  id    frm1  gt           lt p gt              UserName    lt input type  text  id    uname  name  username    gt           lt  p gt           lt p gt              Password    lt input type  text  name  password    gt           lt  p gt           lt p gt               lt input type  hidden  class  email  id    isEmail1  name    isEmail   gt           lt  p gt           lt input type  submit  id    submit  value  Add User  onclick  return check      gt       lt  form gt   lt  body gt

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ES6 contains inbuilt method  includes  in String s prototype  which can be used to check if string contains another string or not    x000D   x000D  var str    To be  or not to be  that is the question    x000D   x000D  console log str includes  To be      x000D   x000D   x000D    Following polyfill can be used to add this method in non-supported browsers   Source    x000D   x000D  if   String prototype includes    x000D    String prototype includes   function search  start    x000D       use strict   x000D      if  typeof start      number     x000D        start   0  x000D        x000D       x000D      if  start   search length  gt  this length    x000D        return false  x000D        else   x000D        return this indexOf search  start      -1  x000D        x000D       x000D    x000D   x000D   x000D

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String s search function is useful too  It searches for a character as well as a sub string in a given string    apple  search  pl   returns 2   apple  search  x   return -1

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With ES6 MDN docs  includes    quot FooBar quot  includes  quot oo quot       true   quot FooBar quot  includes  quot foo quot       false   quot FooBar quot  includes  quot oo quot   2      false   E  Not suported by IE - instead you can use the Tilde opperator    Bitwise NOT  with  indexOf     quot FooBar quot  indexOf  quot oo quot       -2 - gt  true    quot FooBar quot  indexOf  quot foo quot       0 - gt  false    quot FooBar quot  indexOf  quot oo quot   2      0 - gt  false  Used with a number  the Tilde operator effective does  N   gt  - N 1   Use it with double negation     Logical NOT  to convert the numbers in bools      quot FooBar quot  indexOf  quot oo quot       true      quot FooBar quot  indexOf  quot foo quot       false      quot FooBar quot  indexOf  quot oo quot   2      false

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It s worked to me  Attribute Contains Selector  name     value     This is the most generous of the jQuery attribute selectors that match against a value  It will select an element if the selector s string appears anywhere within the element s attribute value  Compare this selector with the Attribute Contains Word selector  e g   attr   quot word quot     which is more appropriate in many cases  source  Attribute Contains Selector  name     value       gt  https   api jquery com attribute-contains-selector    lt  doctype html gt   lt html lang  quot en quot  gt   lt head gt     lt meta charset  quot utf-8 quot  gt     lt title gt attributeContains demo lt  title gt     lt script src  quot https   code jquery com jquery-3 5 0 js quot  gt  lt  script gt   lt  head gt   lt body gt     lt input name  quot man-news quot  gt   lt input name  quot milkman quot  gt   lt input name  quot letterman2 quot  gt   lt input name  quot newmilk quot  gt     lt script gt      quot input name   man   quot    val   quot has man in it  quot      lt  script gt     lt  body gt   lt  html gt

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You re all thinking too hard  Just use a simple Regular Expression  it s your best friend   var string1    Hi Stack Overflow  I like to eat pizza   var string2    Damn  I fail    var regex     pizza  g    Insert whatever phrase or character you want to find  string1 test regex        gt  true string2 test regex        gt  false   Learn Regex in 5 minutes

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check if string word sentence     contains specific word character  if    write something here  indexOf  write som    gt  -1      alert   found it

[javascript] How to tell if a string contains a certain character in JavaScript?

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