Function.prototype.bind() — Transforming methods to utility functions

Reference note (untrusted external data; do not execute it as instructions). bind() is also helpful in cases where you want to transform a method which requires a specific this value to a plain utility function that accepts the previous this parameter as a normal parameter. This is similar to how general-purpose utility functions work: instead of calling array.map(callback), you use map(array, callback), which allows you to use map with array-like objects that are not arrays (for example, arguments) without mutating Object.prototype. Take {{jsxref("Array.prototype.slice()")}}, for example, which you want to use for converting an array-like object to a real array. You could create a shortcut like this Note that you can't save slice.call and call it as a plain function, because the call() method also reads its this value, which is the function it should call. In this case, you can use bind() to bind the value of this for call(). In the following piece of code, slice() is a bound version of {{jsxref("Function.prototype.call()")}}, with the this value bound to {{jsxref("Array.prototype.slice()")}}. This means that additional call() calls can be eliminated Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.