How to Compare Two Arrays in Javascript

Feb 12, 2021 ยท 1 min read
posted in javascript

comparing two different fruits

I recently came across a situation where I needed to compare two arrays in Javascript. I was confused why my comparison returned false, so I created a quick console log test.

console.log([0] === [0]) // false

I struggled to understand this for a moment. I remembered that almost everything in Javascript is a function or an object and an array is just an object which inherits from Array with some special methods.

javascript array object

There isn't an 'equal' method for Javascript arrays. I'll do a separate post on this.

We can compare two arrays in Javascript by converting them to strings.

console.log(JSON.stringify([0]) === JSON.stringify([0])) // true

This works for a basic example. What if the items in the array are in a different order?

a = ['test', 'test2', 'test3']
b = ['test', 'test3', 'test2']

console.log(JSON.stringify(a) === JSON.stringify(b)) // false

We'll have to sort them both before converting them to strings.

a = ['test', 'test2', 'test3']
b = ['test', 'test3', 'test2']

console.log(JSON.stringify(a.sort()) === JSON.stringify(b.sort())) // true

Let's make this more useable.

a = ['test', 'test2', 'test3']
b = ['test', 'test3', 'test2']

const equal = (a, b) => {
    return JSON.stringify(a.sort()) === JSON.stringify(b.sort())

console.log(equal(a, b))

Some things in Javascript aren't as easy as you'd expect. Now you know how to compare two arrays in Javascript.



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