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.
++ operator is overloaded for two types of operands: number and BigInt. It first coerces the operand to a numeric value and tests the type of it. It performs BigInt increment if the operand becomes a BigInt; otherwise, it performs number increment.
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
let x = 3; const y = x++; // x is 4; y is 3 let x2 = 3n; const y2 = x2++; // x2 is 4n; y2 is 3n
let x = 3; const y = ++x; // x is 4; y is 4 let x2 = 3n; const y2 = ++x2; // x2 is 4n; y2 is 4n
|ECMAScript Language Specification |
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