Array() vs new Array()

Question

What is the difference (if there is any) between

x = Array()

and

x = new Array()

Which one should I use?

Answer 1

The spec says:

When Array is called as a function rather than as a constructor, it creates and initialises a new Array object. Thus the function call Array(…) is equivalent to the object creation expression new Array(…) with the same arguments.

Answer 2

You should use the literal []. Reasons are outlined here. Using the Array() constructor can be ambiguous, since it accepts either a length or a list of elements:

new Array(5)   // [ , , , , ]
new Array('5') // ['5']

[5]   // [5]
['5'] // ['5']

The reason you can use Array without the new operator is that internally it does a common trick with constructors:

function Thing(){
    if (!(this instanceof Thing)){
        return new Thing()
    }
    // ... define object
}

That is, if you call Thing() it will call new Thing() for you.

Answer 3

I believe that both are equivalent. However, in JavaScript at least, you should always use the literal syntax:

x = []

But based on some tests in the browsers I have, Array(1, 2, 3) gives the same result as new Array(1, 2, 3), and same with Array(15) and new Array(15). Or just plain new Array().