JavaScript: Should I use new Array()?

Whenever you want to declare an array with predefined elements, I recommend using the first method and to define the elements of the array within square brackets.

Of course, one advantage is that you do not have to write that much and that the code becomes more clear. But there are also other arguments, not to use new Array() in this case. Let us have a look at the following sample:

var arr = new Array(10);

What does this code do? Is it creating an array containing the element 10? No. Here, we are creating an empty array with 10 elements. Although new Array(10, 11) is creating an array containing the two elements 10 and 11, new Array(10) is creating an empty array containing 10 undefined elements. If we had written "arr = [10]", this would not have happened.

With this, we are at the point at which new Array() makes sense: Every time, we would like to create a new empty array of a specified length, we can use new Array() without any problems. For example, if we want to fill the array later in our code or if we cannot define all elements at the same point.

In summary, I recommend to use the writing with square brackets every time you are using predefined arrays and to use new Array() only if you need an array with out predefined elements and you would like to fill the array later.
2015-08-03 at 18:34