How to check if a string starts with another string using vanilla JS

Today, we’re going to look at how to check if a string starts with a specific substring of characters.

Let’s dig in.

The String.startsWith() method

Let’s say you have a string, and you want to check if it starts with Hello.

You can use the String.startsWith() method to do that. Call it on the string you want to test and pass in the string you want to check for. It will return a boolean (true/false).

Here’s an example.

// The string
var str = 'Hello universe';

// Check if the string starts with "Hello"
// returns true
str.startsWith('Hello');

The String.startsWith() method is case-sensitive. If you checked for hello in the example above, it would return false instead of true.

// Check if the string starts with "hello"
// returns false
str.startsWith('hello');

Starting further into the string

You can optionally pass in a second argument, position. If you do, the startsWith() method will start searching that number of characters in.

// returns false
str.startsWith('Hello', 6);

// returns true
str.startsWith('universe', 6);

Browser compatibility

This works in all modern browsers, but not IE. You can polyfill it back to at least IE6.