How to check if a string "StartsWith" another string?

javascript string startswith
sol picture sol · Mar 14, 2009 · Viewed 959.4k times · Source

How would I write the equivalent of C#'s String.StartsWith in JavaScript?

var haystack = 'hello world';
var needle = 'he';

haystack.startsWith(needle) == true

Note: This is an old question, and as pointed out in the comments ECMAScript 2015 (ES6) introduced the .startsWith method. However, at the time of writing this update (2015) browser support is far from complete.

Answer

Christian C. Salvadó picture Christian C. Salvadó · Mar 14, 2009

You can use ECMAScript 6's String.prototype.startsWith() method, but it's not yet supported in all browsers. You'll want to use a shim/polyfill to add it on browsers that don't support it. Creating an implementation that complies with all the details laid out in the spec is a little complicated. If you want a faithful shim, use either:

Once you've shimmed the method (or if you're only supporting browsers and JavaScript engines that already have it), you can use it like this:

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

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

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