Boolean.prototype.toString()

The toString() method returns a string representing the specified boolean value.

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Syntax

js

toString()

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 [@@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 Language Specification
# sec-boolean.prototype.tostring

Browser compatibility

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See also