Question

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What’s the difference between “Array()” and “[]” while declaring a JavaScript array?

In JavaScript you can create a new array like:

var arr = new Array();

or like:

var arr2 = [];

What is the difference and why would you do one over the other?

Answer 1

new Array(2) proudces an array of size 2, containing two undefineds. [2] produces an array of size 1, containing number 2. new Array IMO doesn’t fit with the spirit of JavaScript, even though it may make array construction much more findable. That may or may not be of any importance (I use literals almost exclusively in JavaScript for all applicable types, and I’ve authored/maintained large pieces of JavaScript [30-50 KLOC] successfully).

edit I guess the reasons seasoned javascript programmers avoid new Array syntax are:

• it doesn’t behave uniformly across argument numbers and types ((new Array(X)).length == 1 for any X as long as typeof(X) != "number"
• it’s more verbose and the only thing you gain is the irregularity