Is there a better way to do optional function parameters in JavaScript? [duplicate]

Answer 1

In ECMAScript 2015 (aka "ES6") you can declare default argument values in the function declaration:

function myFunc(requiredArg, optionalArg = 'defaultValue') {
    // do stuff
}

More about them in this article on MDN.

This is currently only supported by Firefox, but as the standard has been completed, expect support to improve rapidly.

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EDIT (2019-06-12):

Default parameters are now widely supported by modern browsers.
All versions of Internet Explorer do not support this feature. However, Chrome, Firefox, and Edge currently support it.