Boolean.prototype.toString() - JavaScript | MDN
Try it
const flag1 = new Boolean(true);
console.log(flag1.toString());
// Expected output: "true"
const flag2 = new Boolean(1);
console.log(flag2.toString());
// Expected output: "true"
Syntax
Parameters
None.
Return value
A string representing the specified boolean value.
Description
The Boolean object overrides the toString method of Object; it does not inherit
Object.prototype.toString(). For Boolean values, the toString method returns a string representation of the boolean value, which is either "true" or "false".
The toString() method requires its this value to be a Boolean primitive or wrapper object. It throws a TypeError for other this values without attempting to coerce them to boolean values.
Because Boolean doesn't have a [Symbol.toPrimitive]() method, JavaScript calls the toString() method automatically when a Boolean object is used in a context expecting a string, such as in a template literal. However, boolean primitive values do not consult the toString() method to be coerced to strings — rather, they are directly converted using the same algorithm as the initial toString() implementation.
js
Boolean.prototype.toString = () => "Overridden";
console.log(`${true}`); // "true"
console.log(`${new Boolean(true)}`); // "Overridden"
Examples
Using toString()
js
const flag = new Boolean(true);
console.log(flag.toString()); // "true"
console.log(false.toString()); // "false"
Specifications
| Specification |
|---|
| ECMAScript® 2027 Language Specification # sec-boolean.prototype.tostring |