Exponentiation (**)
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.
Try it
Syntax
x ** y
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.
For example, -2 ** 2
is 4 in Bash, but is -4 in other languages (such as Python). This is invalid in JavaScript, as the operation is ambiguous. You have to parenthesize either side — for example, as -(2 ** 2)
— to make the intention unambiguous.
Note that some programming languages use the caret symbol ^ for exponentiation, but JavaScript uses that symbol for the bitwise logical XOR operator.
NaN ** 0
(and the equivalent Math.pow(NaN, 0)
) is the only case where NaN
doesn't propagate through mathematical operations — it returns 1
despite the operand being NaN
. In addition, the behavior where base
is 1 and exponent
is non-finite (±Infinity or NaN
) is different from IEEE 754, which specifies that the result should be 1, whereas JavaScript returns NaN
to preserve backward compatibility with its original behavior.
Examples
Basic exponentiation
2 ** 3; // 8
3 ** 2; // 9
3 ** 2.5; // 15.588457268119896
10 ** -1; // 0.1
NaN ** 2; // NaN
NaN ** 0; // 1
1 ** Infinity; // 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
Specification |
---|
ECMAScript Language Specification # sec-exp-operator |
Browser compatibility
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