JS: Triple Equal Operator

Compare Primitives

Triple Equal can compare all Primitive Values except NaN.

"x" === "x"

3 === 3

3 === 3.0

<span class="constant">Infinity</span> === <span class="constant">Infinity</span>

(<span class="constant">NaN</span> === <span class="constant">NaN</span>) === <span class="constant">false</span>

to test if a value is NaN use

• Object.is
• Number.isNaN

Test Object Equality by Triple Equal

Objects (including Array) cannot be compared with triple equal.

When a object is assigned to a variable, the variable holds a reference to the object.

If 2 variables hold the same reference, they are equal.

const x = { "a": 3 };
const y = x; // x and y holds the same reference
console.log(x === y);

but 2 objects with same property values, are still considered different if they have different reference.

// Objects cannot be compared with triple equal

console.log(([] === []) === false);
console.log(({} === {}) === false);
console.log(({ "a": 3 } === { "a": 3 }) === false);

to test equality of objects, see JS: Test Equality of Array and Object by Content 💠

No Auto Type Conversion

Triple equal does not convert Value Types implicitly.

("0" === 0) === false