How to check if a string contains a substring in JavaScript

How to check if a string contains a substring in JavaScript

There are multiple ways to check if a string contains a substring in JavaScript. You can use either String.includes(), String.indexOf(), String.search(), String.match(), regular expressions, or 3rd-party library like Lodash.

String.includes() Method

The String.includes()provides the most simple and popular way to check if a string contains a substring in modern JavaScript.

It was introduced in ES6 and works in all modern browsers except Internet Explorer. The String.includes() method returns true if the string contains the specified substring. Otherwise, it returns false.

Here is an example:

let str = 'MongoDB, Express, React, Node'

str.includes('MongoDB') //true
str.includes('Java') //false
str.includes('Node') //true

Note that includes() is case-sensitive and accepts an optional second parameter, an integer, which indicates the position where to start searching for.

let str = 'MongoDB, Express, React, Node'

str.includes('express') // false (Due to case-sensitive)
str.includes('React', 5) // true

Read this article to learn more about the String.includes() method in JavaScript.

String.indexOf() Method

The String.indexOf() method returns the index of the first occurrence of the substring. If the string does not contain the given substring, it returns -1.

The indexOf() method is case-sensitive and accepts two parameters. The first parameter is the substring to search for, and the second optional parameter is the index to start the search from (the default index is 0).

let str = 'MongoDB, Express, React, Node'

str.indexOf('MongoDB') !== -1 // true
str.indexOf('Java') !== -1 // false
str.indexOf('Node', 5) !== -1 // true

To learn more about the String.indexOf() method, read this guide.

String.search() Method

The String.search() method searches the position of the substring in a string and returns the position of the match.

The search value can be a string or a regular expression. It returns -1 if no match is found.

let str = 'MongoDB, Express, React, Node'

str.search('MongoDB') !== -1 // true
str.search('Java') !== -1 // false
str.search(/node/i) !== -1 // true where i is the case insensitive modifier

String.match() Method

The String.match() method accepts a regular expression as a parameter and searches the string for a match. If it finds the matches, it returns an object, and null if no match is found.

let str = 'MongoDB, Express, React, Node'

str.match(/MongoDB/)
// ['MongoDB', index: 0, input: 'MongoDB, Express, React, Node', groups: undefined]

str.match(/Java/) // null
str.match(/MongoDB/g) !== null // true
str.match(/Java/g) !== null // false
str.match(/node/i) !== null // true where i is the case insensitive modifier

RegExp.test() Method

The RegExp.test() method executes a search for a match between a regular expression and a specified string. It returns true if it finds a match. Otherwise, it returns false.

let str = 'MongoDB, Express, React, Node'

const exp = new RegExp('MongoDB', 'g')
exp.test(str) // true

/Java/g.test(str) // false
/node/i.test(str) // true where i is the case insensitive modifier 

Lodash _.includes() Method

Lodash is a third-party library that provides _.includes() method to check the presence of a substring in a string. This method returns true if a match is found, otherwise, false.

let str = 'MongoDB, Express, React, Node'

_.includes(str, 'MongoDB') // true
_.includes(str, 'Java') // false
_.includes(str, 'Node') // true

let str = 'MongoDB, Express, React, Node'

str.includes('MongoDB') //true
str.includes('Java') //false
str.includes('Node') //true

let str = 'MongoDB, Express, React, Node'

str.includes('express') // false (Due to case-sensitive)
str.includes('React', 5) // true

let str = 'MongoDB, Express, React, Node'

str.indexOf('MongoDB') !== -1 // true
str.indexOf('Java') !== -1 // false
str.indexOf('Node', 5) !== -1 // true

let str = 'MongoDB, Express, React, Node'

str.search('MongoDB') !== -1 // true
str.search('Java') !== -1 // false
str.search(/node/i) !== -1 // true where i is the case insensitive modifier

let str = 'MongoDB, Express, React, Node'

str.match(/MongoDB/)
// ['MongoDB', index: 0, input: 'MongoDB, Express, React, Node', groups: undefined]

str.match(/Java/) // null
str.match(/MongoDB/g) !== null // true
str.match(/Java/g) !== null // false
str.match(/node/i) !== null // true where i is the case insensitive modifier

let str = 'MongoDB, Express, React, Node'

const exp = new RegExp('MongoDB', 'g')
exp.test(str) // true

/Java/g.test(str) // false
/node/i.test(str) // true where i is the case insensitive modifier 

let str = 'MongoDB, Express, React, Node'

_.includes(str, 'MongoDB') // true
_.includes(str, 'Java') // false
_.includes(str, 'Node') // true

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