How do you check if a string contains a character javascript?

Examples

Check if a string includes "world":

let text = "Hello world, welcome to the universe.";
let result = text.includes("world");

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let text = "Hello World, welcome to the universe.";
let result = text.includes("world", 12);

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More examples below.

Definition and Usage

The includes() method returns true if a string contains a specified string.

Otherwise it returns false.

The includes() method is case sensitive.

Syntax

string.includes(searchvalue, start)

Parameters

Return Value

More Examples

Start at position 12:

let text = "Hello world, welcome to the universe.";
let result = text.includes("world", 12);

Try it Yourself »

Browser Support

includes() is an ECMAScript6 (ES6) feature.

ES6 (JavaScript 2015) is supported in all modern browsers:

includes() is not supported in Internet Explorer 11 (or earlier).

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?

Dov Miller

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asked Dec 14, 2010 at 21:35

Vivian RiverVivian River

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4

With ES6 MDN docs .includes()

"FooBar".includes("oo"); // true

"FooBar".includes("foo"); // false

"FooBar".includes("oo", 2); // false

E: Not suported by IE - instead you can use the Tilde opperator ~ (Bitwise NOT) with .indexOf()

~"FooBar".indexOf("oo"); // -2 -> true

~"FooBar".indexOf("foo"); // 0 -> false

~"FooBar".indexOf("oo", 2); // 0 -> false

Used with a number, the Tilde operator effective does ~N => -(N+1). Use it with double negation !! (Logical NOT) to convert the numbers in bools:

!!~"FooBar".indexOf("oo"); // true

!!~"FooBar".indexOf("foo"); // false

!!~"FooBar".indexOf("oo", 2); // false

 

domster

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answered Jun 15, 2017 at 22:26

3

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.

answered Dec 14, 2010 at 21:38

cdhowiecdhowie

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0

check if string(word/sentence...) contains specific word/character

if ( "write something here".indexOf("write som") > -1 )  { alert( "found it" );  } 

answered Apr 11, 2013 at 7:02

T.ToduaT.Todua

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1

ES6 contains inbuilt method (includes) in String's prototype, which can be used to check if string contains another string or not.

var str = 'To be, or not to be, that is the question.';

console.log(str.includes('To be')); 

Following polyfill can be used to add this method in non-supported browsers. (Source)

if (!String.prototype.includes) {
  String.prototype.includes = function(search, start) {
    'use strict';
    if (typeof start !== 'number') {
      start = 0;
    }
    
    if (start + search.length > this.length) {
      return false;
    } else {
      return this.indexOf(search, start) !== -1;
    }
  };
}

answered Dec 3, 2017 at 9:55

Vipin KumarVipin Kumar

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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); // => true
string2.test(regex); // => false

Learn Regex in 5 minutes?

answered Oct 3, 2014 at 14:44

Adam McArthurAdam McArthur

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5

Use a regular expression to accomplish this.

function isAlphanumeric( str ) {
 return /^[0-9a-zA-Z]+$/.test(str);
}

answered Dec 14, 2010 at 21:41

Gabriele PetrioliGabriele Petrioli

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2

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

answered Jul 13, 2018 at 13:49

Ejaz KarimEjaz Karim

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0

var inputString = "this is home";
var findme = "home";

if ( inputString.indexOf(findme) > -1 ) {
    alert( "found it" );
} else {
    alert( "not found" );
}

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 ($).

answered Dec 14, 2010 at 21:45

fairfieldtfairfieldt

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0

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) >= 0;

Taki

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answered Nov 9, 2015 at 9:43

1

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/

answered Nov 28, 2013 at 21:01

Oliver NiOliver Ni

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0

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

answered May 4, 2015 at 14:32

learner010learner010

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If you are reading data from the DOM such as a p or h2 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

Text you need to read one
Text you need to read two
Text you need to read three

JS

let paras = document.querySelectorAll('p');

paras.forEach(p => {
  if(p.textContent.includes('T')){
       p.remove();
    } 
});

answered Feb 2, 2019 at 1:24

0

Working perfectly.This exmple will help alot.

    
My form 
    

        

            UserName : 
        
        

            Password : 
        
        

            
        
        
    

chriz

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answered Aug 7, 2013 at 11:56

MankitaPMankitaP

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You can use string.includes(). Example:

var string = "lorem ipsum hello world";
var include = "world";
var a = document.getElementById("a");

if (string.includes(include)) {  
  alert("found '" + include + "' in your string");
  a.innerHTML = "found '" + include + "' in your string";
}

answered Feb 20 at 3:44

A sample regex pattern test you can use to find out if the string contains a character '@':

/(@[A-Za-z])\w+/.test(str_text)

answered Jun 21, 2021 at 14:16

shasi kanthshasi kanth

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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 > 47 && code < 58) ||
    // A-Z
    (code > 64 && code < 91) ||
    // a-z
    (code > 96 && code < 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) &&
      !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('你好'));

assert( is_almost_alphanumeric('aB0'));
assert( is_almost_alphanumeric('aB0_-'));
assert(!is_almost_alphanumeric('aB0_-*'));
assert(!is_almost_alphanumeric('你好'));

GitHub upstream.

Tested in Node.js v10.15.1.

answered Oct 12, 2019 at 22:30

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~="word"]), which is more appropriate in many cases.

source: Attribute Contains Selector [name*=”value”] => https://api.jquery.com/attribute-contains-selector/

answered Feb 12, 2021 at 1:51

1

The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate.

const array1 = [1, 2, 3];

console.log(array1.includes(2));
// expected output: true

const pets = ['cat', 'dog', 'bat'];

console.log(pets.includes('cat'));
// expected output: true

console.log(pets.includes('at'));
// expected output: false

know more

answered Sep 2, 2021 at 21:04

Demonstration: The include() method finds the “contains” character in whole string, it will return a true.

var string = "This is a tutsmake.com and this tutorial contains javascript include() method examples."

str.includes("contains");

//The output of this

  true

answered Sep 2, 2019 at 10:48

DeveloperDeveloper

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