JavaScript Boolean prototype
Example
Make a new method for JavaScript booleans:
Boolean.prototype.myColor = function() {
if (this.valueOf() == true) {
return "green";
} else {
return = "red";
}
};
Create a boolean, then call myColor():
let a = true;
let color = a.myColor();
Try it Yourself »
Definition and Usage
prototype allows you to add new properties and methods to booleans.
prototype is a property available with all JavaScript objects.
Syntax
Boolean.prototype.name = value
Warning
You are not advised to change the prototype of an object that you do not control.
You should not change the prototype of built in JavaScript datatypes like:
- Numbers
- Strings
- Arrays
- Dates
- Booleans
- Function
- Objects
Only change the prototype of your own objects.
The prototype Property
The JavaScript prototype property allows you to add new properties to objects:
Example
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.eyeColor = eyecolor;
}
Person.prototype.nationality = "English";
Try it Yourself »
Browser Support
prototype is an ECMAScript1 (ES1) feature.
ES1 (JavaScript 1997) is fully supported in all browsers:
| Chrome | Edge | Firefox | Safari | Opera | IE |
| Yes | Yes | Yes | Yes | Yes | Yes |
