ECMAScript 6 introduced String.prototype.includes:
const string = "foo";
const substring = "oo";
console.log(string.includes(substring)); // trueString.prototype.includes is case-sensitive and is not supported by Internet Explorer without a polyfill.
In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:
var string = "foo";
var substring = "oo";
console.log(string.indexOf(substring) !== -1); // trueMDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › String › includes
String.prototype.includes() - JavaScript | MDN
The includes() method of String values performs a case-sensitive search to determine whether a given string may be found within this string, returning true or false as appropriate.
W3Schools
w3schools.com › jsref › jsref_includes.asp
JavaScript String includes() Method
❮ Previous JavaScript String ... text.includes("world"); Try it Yourself » · More examples below. The includes() method returns true if a string contains a specified string....
How to check whether a string contains a substring in JavaScript? - Stack Overflow
Example: es6 includes returns false for "abc".includes("ab", "1") this polyfill will return true 2021-02-02T15:34:57.623Z+00:00 ... Another alternative is KMP (Knuth–Morris–Pratt). The KMP algorithm searches for a length-m substring in a length-n string in worst-case O(n+m) time, compared to a worst-case of O(n⋅m) for the naive algorithm, so using KMP may be reasonable if you care about worst-case time complexity. Here's a JavaScript ... More on stackoverflow.com
contains vs includes javascript?
There's no 'contains' method on strings in Javascript . More on reddit.com
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September 7, 2018Why includes() works with a string?
Hello, In MDN doc : " The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate." But If I use a string: let string = 'string' console.log(str… More on forum.freecodecamp.org
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February 21, 2022(Silly?) inferencing issue/question for Array.includes()
There is a difference between Array and Array | Array (and it's similar with other generics). includes method for the former requires type A | B while for the latter A & B. That's been an issue for years now - don't have a GitHub issue link right now, as I'm on mobile, but should be easily findable. Will post more explanation once I get in front of my PC More on reddit.com
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January 25, 2022Videos
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JavaScript Basics - includes()
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What is the .includes() String Method? | JavaScript in LESS-THAN ...
Educative
educative.io › answers › what-is-stringincludes-method-in-javascript
What is String.includes() method in JavaScript?
The string.includes() method is used to find out if a string contains a particular substring.
Career Karma
careerkarma.com › blog › javascript › javascript string contains: step-by-step guide
JavaScript String Contains: Step-By-Step Guide | Career Karma
December 1, 2023 - In this tutorial, we’re going ... JavaScript includes() method, introduced in ES6, determines whether a string contains the characters you have passed into the method....
Mimo
mimo.org › glossary › javascript › includes-method
JavaScript includes() method: Syntax, Usage, and Examples
The JavaScript includes method helps you quickly determine if a string contains a substring or if an array contains a value. It’s an essential tool in modern JavaScript—cleaner than index-based methods, easier to read, and ideal for conditions, filters, and validation.
Top answer 1 of 3
16083
ECMAScript 6 introduced String.prototype.includes:
const string = "foo";
const substring = "oo";
console.log(string.includes(substring)); // trueString.prototype.includes is case-sensitive and is not supported by Internet Explorer without a polyfill.
In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:
var string = "foo";
var substring = "oo";
console.log(string.indexOf(substring) !== -1); // true 2 of 3
803
There is a String.prototype.includes in ES6:
"potato".includes("to");
> true
Note that this does not work in Internet Explorer or some other old browsers with no or incomplete ES6 support. To make it work in old browsers, you may wish to use a transpiler like Babel, a shim library like es6-shim, or this polyfill from MDN:
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;
}
};
}
TechOnTheNet
techonthenet.com › js › string_includes.php
JavaScript: String includes() method
This JavaScript tutorial explains how to use the string method called includes() with syntax and examples. In JavaScript, includes() is a string method that determines whether a substring is found in a string.
GeeksforGeeks
geeksforgeeks.org › javascript › check-an-array-of-strings-contains-a-substring-in-javascript
Check If An Array of Strings Contains a Substring in JavaScript - GeeksforGeeks
1 week ago - The includes() method returns true if the string contains 'eks'.
Reddit
reddit.com › r/learnjavascript › contains vs includes javascript?
r/learnjavascript on Reddit: contains vs includes javascript?
September 7, 2018 -
Please which one should I use since the two seems to look for a substring in a specific string?
thanks for any hint
Medium
medium.com › nerd-for-tech › basics-of-javascript-string-includes-method-107b6094f00b
Basics of Javascript · String · includes() (method) | by Jakub Korch | Nerd For Tech | Medium
June 4, 2021 - The includes() method performs a case-sensitive search to determine whether a specified string may be found within the searched string. Returning value can either be true or false based on a result of search.
freeCodeCamp
forum.freecodecamp.org › javascript
Why includes() works with a string? - JavaScript - The freeCodeCamp Forum
February 21, 2022 - Hello, In MDN doc : " The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate." But If I use a string: let string = 'string' console.log(str…
JavaScript in Plain English
javascript.plainenglish.io › 10-ways-to-check-if-a-string-contains-substring-in-javascript-91639d81b7
10 Ways To Check If A String Contains Substring In JavaScript | by Sam C. Tomasi | JavaScript in Plain English
November 23, 2022 - const string = "Hello World!"; const substring = "HeLLo"; console.log(string.toLowerCase().includes(substring.toLowerCase())); // true ... New JavaScript and Web Development content every day.
PTC Community
community.ptc.com › t5 › ThingWorx-Developers › Using-includes-on-a-string-never-works › td-p › 628132
Solved: Using .includes() on a string never works - PTC Community
September 24, 2019 - Whenever I attempt to use the '.includes()' method on string in ThingWorx composer, I always get an error saying that the .includes method can not be found on the object. I even log the type of the variable that I am trying to edit, just to make sure it is in fact a string.
Sentry
sentry.io › sentry answers › javascript › how to check whether a string contains a substring in javascript?
How to Check Whether a String Contains a Substring in JavaScript? | Sentry
You can use JavaScript’s includes() method to check whether a string contains a substring.
tutorialstonight
tutorialstonight.com › javascript-string-includes
JavaScript String includes(): Check if string have a substring
The method is applied on a string and the search string is passed as an argument in the method, if the calling string contains the search string then it returns true else returns false. Note: The includes() method is case-sensitive.
Programiz
programiz.com › javascript › library › string › includes
Javascript String includes()
// check if message includes the string "Java" let result = message.includes("Java"); console.log(result); // Output: true
TutorialsPoint
tutorialspoint.com › home › javascript › javascript string includes method
JavaScript String Includes Method
September 1, 2008 - The JavaScript String includes() method searches for the part of the string and determines whether the specified string is found in the original string.
Reality Ripple
udn.realityripple.com › docs › Web › JavaScript › Reference › Global_Objects › String › includes
String.prototype.includes() - JavaScript
if (!String.prototype.includes) { String.prototype.includes = function(search, start) { 'use strict'; if (search instanceof RegExp) { throw TypeError('first argument must not be a RegExp'); } if (start === undefined) { start = 0; } return this.indexOf(search, start) !== -1; }; }
GeeksforGeeks
geeksforgeeks.org › javascript › javascript-string-includes-method
JavaScript String includes() Method - GeeksforGeeks
The includes() method is used to check whether a string contains a specific value. It returns a boolean result based on whether the text is found or not. Returns true if the string contains the specified value.
Published January 16, 2026
Tabnine
tabnine.com › home › how to use the includes() method in javascript
How to Use the includes() Method in JavaScript - Tabnine
July 25, 2024 - The includes() method is part of both the Array and String prototypes. This method accepts a search value as a parameter, and returns true if the value is either contained in the array on which it is called, or if it exists as a substring of the string object on which it is called...