Boolean.prototype.toString()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The toString()
method of Boolean
values returns a string representing the specified boolean value.
Try it
Syntax
toString()
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.
Boolean.prototype.toString = () => "Overridden";
console.log(`${true}`); // "true"
console.log(`${new Boolean(true)}`); // "Overridden"
Examples
Using toString()
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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