Baseline Widely available
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 function (without new), it returns value coerced to a number primitive. Specially, BigInts values are converted to numbers instead of throwing. If value is absent, it becomes 0.
When Number() is called as a constructor (with new), it uses the coercion process above and returns a wrapping Number object, which is not a primitive.
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
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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