What are usages of "prototype" properties in javascript

Question

prototype in javascript

Answer 1

All instances of a type have all prototype methods defined. 'this' holds the value of the current instance.

Number.prototype.squared=function() {
return this**2;
}
var a = 4; // 4 is an instance of Number
a.squared(); // 16

// Also works with instances generated by the 'new' keyword
var a = function(string) {
this.string = string;
}
a.prototype.getString=function() {
return this.string;
}
b = new a("abc");
alert(b.getString()); // abc

Answer 2

thank you Draphar. so prototype is used to add additional properties to the object or function. can we modify the property using prototype.

Answer 3

Sorry, the direct manipulation of the value is not possible, only for native methods like .reverse() for arrays. I can't say

String.prototype.change = function (number){
this = number; // 'Invalid left-hand sign in assignment', which means 'can not change the value on the left'
}
"abc".change(1);

But you can return new values
String.prototype.add = function (number){
return parseInt(this) + number;
}
"3".add(4); // 7

Answer 4

thank you Draphar