Find out the difference between primitives and objects in JavaScript in my blog post here.

Let's start by comparing some arrays and objects.

[] === []; //false

{} === {}; //false

["apple"] === ["apple"]; //false

{key: "value"} === {key: "value"}; //false

The results are false because we are comparing two different instances of arrays and objects.

Note: writing [] is the same as creating a new instance of Array and writing {} is the same as creating a new instance of Object.

We can create a new array instance using new Array() and we can create a new object instance using new Object(). So, even if we change the arrays and objects examples in the previous example to the new syntax, we get the same result.

new Array() === new Array() //false

new Object() === new Object() //false

Object assignment

const nums_array_one = [1, 2, 3, 4]

// nums_array_two now points to nums_array_one
const nums_array_two = nums_array_one

console.log(nums_array_one === nums_array_two) //true

When we assigned the nums_array_two variable to nums_array_one, we did not create a copy of nums_array-one. nums_array_two simply created a reference to nums_array_one. In other words, nums_array_one & nums_array_two point to the same location in memory.

This is why nums_array_one === nums_array_two is equal to true as we are comparing the same instance of the array.