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JavaScript Equality Operators

Published May 31 2019

Those operators accept two values and return a boolean:

Let’s talk what we mean for strict. Without the strict check, the second operand is converted to the type of the first before making the comparison. Strict prevents this.


const a = true

a == true //true
a === true //true

1 == 1 //true
1 == '1' //true
1 === 1 //true
1 === '1' //false

You cannot check objects for equality: two objects are never equal to each other. The only case when a check might be true is if two variables reference the same object.

Some peculiarities to be aware: NaN is always different from NaN.

NaN == NaN //false

null and undefined values are equal if compared in non-strict mode:

null == undefined //true
null === undefined //false

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