JavaScript - Booleans

Everything Without a "Value" is False

The Boolean value of 0 (zero) is false

<p id="demo"></p>

<script>
let x = 0;
document.getElementById("demo").innerHTML = Boolean(x);
</script>

false

 

 

The Boolean value of -0 (minus zero) is false.

<p id="demo"></p>

<script>
let x = -0;
document.getElementById("demo").innerHTML = Boolean(x);
</script>

false

 

The Boolean value of "" (empty string) is false

<p id="demo"></p>

<script>
let x = "";
document.getElementById("demo").innerHTML = Boolean("");
</script>

false

 

The Boolean value of undefined is false

<p id="demo"></p>

<script>
let x;
document.getElementById("demo").innerHTML = Boolean(x);
</script>

false

 

The Boolean value of null is false

 

The Boolean value of NaN is false

<p id="demo"></p>

<script>
let x = 10 / "Hello";
document.getElementById("demo").innerHTML = Boolean(x);
</script>

false

 

 

 

Booleans as Objects

let x = false;
let y = new Boolean(false);

// typeof x returns boolean
// typeof y returns object

 

 

When using the == operator, x and y are equa.

When using the === operator, x and y are not equal.

let x = false;
let y = new Boolean(false);

Do not create Boolean objects.

objects always return false.