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Object​.is() vs === in JavaScript

In this post you’ll learn how to use the new ES6 method in JavaScript.

What is

Introduced in ECMAScript 2015, known as ES2015 or ES6, allows us to test equality of JavaScript objects (and primitive values, despite the name). is very similar to the JavaScript strict comparison operator === and can almost be used interchangeably (despite some minor differences which we’ll cover).

We won’t discuss the differences between both == and === here, as I’ll assume you know what a strict comparison with === does. A strict comparison performs no type conversion, known as coercion, compared to non-strict (behind the scenes they both perform type coercion, but strict disregards it when evaluating equality).

In its simplest form, we could use with strings, numbers or objects (and much more):

'abc' === 'abc' // true'abc', 'abc') // true

1 === 1 // true, 1) // true

'1' === 1 // false'1', 1) // false

{} === {} // false{}, {}) // false

We’ll momentarily explore the differences between and === as well, as here they act the same!

When using ===, we are performing a value-comparison operation.

When using we are performing a check using the SameValue algorithm, which looks like so:

1. If Type(x) is different from Type(y), return false.
2. If Type(x) is Number or BigInt, then
    a. Return ! Type(x)::sameValue(x, y).
3. Return ! SameValueNonNumeric(x, y).

🕵️‍♀️ Check out the official ECMAScript standard for a deeper syntax guide!

Really, we’re here to answer one question - why should I use over ===?

Differences between and ===

There are two major differences between and the triple equals comparison ===. All other operations with and === will produce the identical result.

The first difference is that -0 and +0 can now be properly compared:

+0 === -0 // true, -0) // false

Really, it comes down to NaN (Not-a-Number) and how it fixes the behaviour when comparing values that could be NaN - such as Number('abc'):

NaN === NaN // false, NaN) // true

Number.NaN === Number.NaN // false, Number.NaN) // true

NaN === Number.NaN // false, Number.NaN) // true

This tells us that was also created to help us to properly distinguish between NaN values (and even the newly added Number.NaN).

We also get the added benefit with the prototype method that it follows a more functional programming style.

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Other Array prototype methods such as Array ForEach and Array Reduce also slot nicely into a functional programming style. However, I will admit the code is likely cleaner using ===, so use what makes sense.

Check out the examples I’ve created above in the live StackBlitz demo:


We’ve covered the new ES6 method and compared it to JavaScript’s strict triple equals statement ===.

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Learning the differences between the two, we can now choose to use as a better comparison check for NaN values, as well as adopting a more functional programming style.

Happy coding!

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