Since the Array constructor is ambiguous in how it deals with its parameters,
it is highly recommended to use the array literal - [] notation -
when creating new arrays.
[1, 2, 3]; // Result: [1, 2, 3]
new Array(1, 2, 3); // Result: [1, 2, 3]
[3]; // Result: [3]
new Array(3); // Result: []
new Array('3') // Result: ['3']
In cases when there is only one argument passed to the Array constructor
and when that argument is a Number, the constructor will return a new sparse
array with the length property set to the value of the argument. It should be
noted that only the length property of the new array will be set this way;
the actual indexes of the array will not be initialized.
var arr = new Array(3);
arr[1]; // undefined
1 in arr; // false, the index was not set
Being able to set the length of the array in advance is only useful in a few cases, like repeating a string, in which it avoids the use of a loop.
new Array(count + 1).join(stringToRepeat);
Literals are preferred to the Array constructor. They are shorter, have a clearer syntax, and increase code readability.