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 | Try it |
|---|---|---|---|
| && | 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:
Note: See Also: JavaScript Comparisons.
