The Number()
constructor creates Number
objects. When called as a function, it returns primitive values of type Number.
The Number()
constructor creates Number
objects. When called as a function, it returns primitive values of type Number.
new Number(value) Number(value)
Note: Number()
can be called with or without new
, but with different effects. See Return value.
value
The numeric value of the object being created.
When Number
is called as a constructor (with new
), it creates a Number
object, which is not a primitive.
When Number
is called as a function, it coerces the parameter to a number primitive. BigInts are converted to numbers. If the value can't be converted, it returns NaN
.
Warning: You should rarely find yourself using Number
as a constructor.
const a = new Number("123"); // a === 123 is false const b = Number("123"); // b === 123 is true a instanceof Number; // is true b instanceof Number; // is false typeof a; // "object" typeof b; // "number"
Number()
is the only case where a BigInt can be converted to a number without throwing, because it's very explicit.
+1n; // TypeError: Cannot convert a BigInt value to a number 0 + 1n; // TypeError: Cannot mix BigInt and other types, use explicit conversions
Number(1n); // 1
Note that this may result in loss of precision, if the BigInt is too large to be safely represented.
BigInt(Number(2n ** 54n + 1n)) === 2n ** 54n + 1n; // false
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Number |
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/Number