How to Determine if a JavaScript String Starts With a Specific Substring?

How to Check if a String Starts With Another String in JavaScript

The String.prototype.startsWith() method in JavaScript allows you to check if a string begins with a specified substring.

Prior to ES6, you could use a polyfill to add startsWith() functionality to unsupported browsers:

Matthias Bynens's String.prototype.startsWith Shim:

if (!String.prototype.startsWith) {
  String.prototype.startsWith = function(searchString, position) {
    position = position || 0;
    return this.substr(position, searchString.length) === searchString;
  };
}

ES6-Shim:

require('es6-shim');

Usage:

Once you have shimmed startsWith() or are using a compatible browser, you can use it as follows:

console.log("Hello World!".startsWith("He"));  // true

var haystack = "Hello world";
var prefix = 'orl';
console.log(haystack.startsWith(prefix));  // false

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