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:
| Oper | Name | Example |
|---|---|---|
| && | AND | (x < 10 && y > 1) is true |
| OR | (x === 5 | y === 5) is false |
| ! | NOT | !(x === y) is true |
JavaScript Logical AND
The && operator returns true if both expressions are true , otherwise false :
Example
let x = 6;
let y = 3;
let z = (x < 10 && y > 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 :
| Chrome 85 | Edge 85 | Firefox 79 | Safari 14 | Opera 71 |
|---|---|---|---|---|
| Aug 2020 | Aug 2020 | Mar 2020 | Sep 2020 | Sep 2020 |
See Also
JavaScript Comparisons .