The problem with includes() is that it requires a string value and therefore you can’t pass an array to it. Includes() is a simple array function which returns true if the passed value matches a value within the array. Look for a single value in an array using includes() If you want to skip straight to the end there are some ready to go ‘inArray’ style JavaScript functions for you to use. This post will explore how you can find out whether a JavaScript array contains certain values using simple functions to evaluate to true or false. I’ve looked at how to find the closest number in a JavaScript array, but what happens when you simply want to check whether a value (or an array of values) exist within that array? Would you like to be able to pass an array to Includes()? Facebook Share Twitter Share LinkedIn Share indexOf ( 'nice', 3 ) != - 1 //false 'a nice string'. indexOf ( 'nice' ) != - 1 //true 'a nice string'. Like includes(), the second parameters sets the starting point: 'a nice string'. If the substring is found, it returns the index of the character that starts the string. Pre-ES6, the common way to check if a string contains a substring was to use indexOf, which is a string method that return -1 if the string does not contain the substring.

includes ( 'nice', 2 ) //true Pre-ES6 alternative to includes(): indexOf() includes ( 'nice', 3 ) //false 'a nice string'. includes ( 'nice' ) //true 'a nice string'. Includes() also accepts an optional second parameter, an integer which indicates the position where to start searching for: 'a nice string'. To use it on all browsers, use Polyfill.io or another dedicated polyfill.

It’s supported in all modern browsers except Internet Explorer: This method was introduced in ES6/ES2015. The most simple one, and also the canonical one going forward, is using the includes() method on a string: 'a nice string'. JavaScript offers different ways to perform this operation. Learn the canonical way, and also find out all the options you have, using plain JavaScriptĬhecking if a string contains a substring is one of the most common tasks in any programming language. JavaScript offers many ways to check if a string contains a substring.

Typescript includes