Updated May 30 2019
Checking if a string contains a substring is one of the most common tasks in any programming language.
The most simple one, and also the canonical one going forward, is using the
includes() method on a string:
'a nice string'.includes('nice') //true
This method was introduced in ES6/ES2015.
It’s supported in all modern browsers except Internet Explorer:
To use it on all browsers, use Polyfill.io or another dedicated polyfill.
includes() also accepts an optional second parameter, an integer which indicates the position where to start searching for:
'a nice string'.includes('nice') //true 'a nice string'.includes('nice', 3) //false 'a nice string'.includes('nice', 2) //true
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. If the substring is found, it returns the index of the character that starts the string.
includes(), the second parameters sets the starting point:
'a nice string'.indexOf('nice') !== -1 //true 'a nice string'.indexOf('nice', 3) !== -1 //false 'a nice string'.indexOf('nice', 2) !== -1 //true
I wrote an entire book on this topic 👇
I also got a super cool course 👇