Increment (++)
The increment (++) operator increments (adds one to) its operand and returns the value before or after the increment, depending on where the operator is placed.
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Syntax
x++
++x
Description
If used postfix, with operator after operand (for example, x++), the increment operator increments and returns the value before incrementing.
If used prefix, with operator before operand (for example, ++x), the increment operator increments and returns the value after incrementing.
The increment operator can only be applied on operands that are references (variables and object properties; i.e. valid assignment targets). ++x itself evaluates to a value, not a reference, so you cannot chain multiple increment operators together.
++(++x); // SyntaxError: Invalid left-hand side expression in prefix operation
Examples
Postfix increment
let x = 3;
const y = x++;
// x = 4
// y = 3
Prefix increment
let x = 3;
const y = ++x;
// x = 4
// y = 4
Specifications
| Specification |
|---|
| ECMAScript Language Specification # sec-postfix-increment-operator |
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