What is the difference between creating an array with Array(0) and array = []?
To my knowledge both are empty Array objects.
array
>>> []
Array(0)
>>> []
But when I compare them they return 'false'.
var array = []
array === Array(0)
>>> false
What's going on here??
To my knowledge both are empty Array objects.
They are
But when I compare them they return 'false'.
When you compare two objects in JavaScript you are testing to see if they are the same object, not if they are identical objects.
Because arrays are objects, not primitives :
var x = 5; // primitive
var y = 5; // primitive
console.log(x == y); // True
var x = [5]; // object
var y = [5]; // object
console.log(x == y); // False
var x = '5'; // primitive
var y = '5'; // primitive
console.log(x == y); // True
var x = {0:5}; // object
var y = {0:5}; // object
console.log(x == y); // FalseAbout the difference, Check this question's answers (The accepted and the second one) : What’s the difference between “Array()” and “[]” while declaring a JavaScript array?
And more on primitives and objects : object vs. primitive
var p = Array(0); // []
[] var p = [] // []
Both work the same way to create an empty array.
var p = Array(3); //[undefined, undefined, undefined]
Which you can also do using :
var p = [undefined, undefined, undefined];
Again both work the same way internally but have different use cases :
For ex. If you want to create an array with n elements :
var array = new Array(n) // [undefined * n]
If you want to initialise values of arrays while creation :
var arry = [1,2,3,4];
One thing to note here is you can create an initialized array with new Array() as well :
var p = new Array(1,2,3,4); // [1,2,3,4]
But when you try to create an array with one initialised value it takes that one parameter and create an array of that size :
var p = new Array(4) // [undefined*4]
var a = new Array(1,2,3,4); as well.
2 arrays (even empty) can't be compared this way and be equal.
Here's the answer how to compare 2 arrays in a proper way: How to compare arrays in JavaScript?
0withinArray(0), that's considered the first element, as opposed to the empty[]which always signifies empty arrays?[] === [] => falseArray(0)means an empty array not an array with0as first element.