JavaScript Logical Operators

Logical operators are used to combine boolean expressions.

Logical operators can be used to modify the results of comparisons.

Typically, you will use a comparison operator to check a condition, and a logical operator to combine conditions into more complex logic.

JavaScript Logical Operators

Logical operators are used to determine the logic between variables or values.

Given that x = 6 and y = 3, the table below explains the logical operators:

JavaScript Logical AND

The && operator returns true if both expressions are true, otherwise false:

Example

let x = 6;

let y = 3;

let z = (x   1)

JavaScript Logical OR

The || operator returns true if one or both expressions are true, otherwise false:

Example

let x = 6;

let y = -3;

let z = (x > 0 || y > 0)

JavaScript Logical NOT

The NOT operator (!) returns true for false expressions and false for true expressions.

Example

let x = (5 == 8);

let y = !(5 == 8)

The Nullish Coalescing Operator (??)

The ?? operator returns the right operand when the left operand is nullish (null or undefined), otherwise it returns the left operand.

Example

let name = null;

let text = "missing";

let result = name ?? text;

When programming, a lot of values can be falsey (like 0, empty strings, false, undefined, null, NaN).

However, sometimes you want to check if a variable is nullish (either undefined or null), like when it is okay for a variable to be an empty string, or a false value. Then you can use the nullish coalescing operator.

Browser Support

?? is an ES2020 feature.

ES2020 is fully supported in all modern browsers since September 2020: