The Number() constructor creates Number objects. When called as a function, it returns primitive values of type Number.
Syntax
new Number(value)
Number(value)
Note:
Number()can be called with or withoutnew, but with different effects. See Return value.
Parameters
value- : The numeric value of the object being created.
Return value
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
Numberas a constructor.
Examples
Creating Number objects
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"
Using Number() to convert a BigInt to a 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