javascript - Array.of vs "[ ]". When to use Array.of over "[ ]"?

Question

I was doing a bit of reading when I found Array.of.

As per MDN,

The Array.of() method creates a new Array instance with a variable number of arguments, regardless of number or type of the arguments.

var a = Array.of(1,2,3,4,5);
console.log(a)

Answer 1

There is one subtle difference between Array.of() and Array() / [] constructor. Normally just like Array(), the this in Array.of() will be the Array object and it will use the Array.constructor which is function Array() to construct it's result.

However Array.of can behave differently by changing it's bound context. If the bound context can be used as a constructor (if the bound object is a function) it will use that function to construct. So let's bind the Array.of() to a function and see what happens.

function Test(n){console.log(n)}
Test.prototype.last = function(){return this[this.length-1]};

var what = Array.of.call(Test, [5,6,7], {a:0,b:1}, 42, null, "this is last");
console.log(JSON.stringify(what,null,2));
console.log(what.last());