Casting

Casting#

The conversion surface across the eight types, plus the == / === contrast.

From / to	How
any to string	`String(x)` or ` `${x}` ` (calls `.toString()`); `JSON.stringify(x)` for objects.
string to number	`Number(s)` (strict; `""` → `0`, `"x"` → `NaN`).
string to integer	`parseInt(s, 10)`; always pass the radix.
string to float	`parseFloat(s)`; lenient, reads the leading float.
any to boolean	`Boolean(x)` or `!!x`.
number to bigint	`BigInt(n)`; `n` must be an integer.
bigint to number	`Number(big)`; precision may be lost.

== triggers implicit coercion (1 == "1" is true); === does not (1 === "1" is false). The operator writes === and !== by default.

Strict equality compares by type and value.

1 === "1";            // false

Loose equality coerces before comparing.

1 == "1";             // true

== null is the one common, defensible loose form; it matches both null and undefined in one comparison.

x == null;            // true for both null and undefined