How Does JavaScript's `String.prototype.startsWith()` Work and How Can I Ensure Browser Compatibility?

Using String.prototype.startsWith() in JavaScript

String manipulation is a crucial aspect of JavaScript development. In certain scenarios, it becomes necessary to determine if one string begins with another. In C#, the String.StartsWith method conveniently aids in performing this operation.

JavaScript Equivalent

JavaScript introduced the String.prototype.startsWith() method in ECMAScript 2015 (ES6). This method evaluates whether a given string commences with a specified prefix, returning a boolean value.

Browser Support

While ES6 introduced String.prototype.startsWith(), browser support for this method varies. As of this writing, most major browsers support it. However, if compatibility with older browsers is a concern, it's advisable to consider using a shim or polyfill.

Shimming for Unsupported Browsers

Two reliable shims can provide String.prototype.startsWith() functionality in unsupported browsers:

• Matthias Bynens's String.prototype.startsWith shim
• The es6-shim, which offers support for a comprehensive range of ES6 features, including String.prototype.startsWith()

Usage

Once the method is shimmed or in browsers that natively support it, using String.prototype.startsWith() is straightforward:

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

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

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