Exponentiation (**) - JavaScript 编辑

The exponentiation operator (**) returns the result of raising the first operand to the power of the second operand. It is equivalent to Math.pow, except it also accepts BigInts as operands.

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Syntax

Operator: var1 ** var2

Description

The exponentiation operator is right-associative: a ** b ** c is equal to a ** (b ** c).

In most languages, such as PHP, Python, and others that have an exponentiation operator (**), the exponentiation operator is defined to have a higher precedence than unary operators, such as unary + and unary -, but there are a few exceptions. For example, in Bash, the ** operator is defined to have a lower precedence than unary operators.

In JavaScript, it is impossible to write an ambiguous exponentiation expression. That is, you cannot put a unary operator (+/-/~/!/delete/void/typeof) immediately before the base number; doing so will cause a SyntaxError.

-2 ** 2;
// 4 in Bash, -4 in other languages.
// This is invalid in JavaScript, as the operation is ambiguous.

-(2 ** 2);
// -4 in JavaScript and the author's intention is unambiguous.

Note that some programming languages use the caret symbol ^ for exponentiation, but JavaScript uses that symbol for the bitwise logical XOR operator.

Examples

Basic exponentiation

2 ** 3   // 8
3 ** 2   // 9
3 ** 2.5 // 15.588457268119896
10 ** -1 // 0.1
NaN ** 2 // NaN

Associativity

2 ** 3 ** 2   // 512
2 ** (3 ** 2) // 512
(2 ** 3) ** 2 // 64

Usage with unary operators

To invert the sign of the result of an exponentiation expression:

-(2 ** 2) // -4

To force the base of an exponentiation expression to be a negative number:

(-2) ** 2 // 4

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Addition operator
• Subtraction operator
• Division operator
• Multiplication operator
• Remainder operator
• Increment operator
• Decrement operator
• Unary negation operator
• Unary plus operator