That means prototype helps us to extend the basic built in types by adding additional properties depending on our need.
For example for strings you may want to define a new method for converting a string into new type of html font tag not already defined by javascript object.
<html>
<head>
<title>Javascript Prototype Object</title>
<script type="text/javascript">
function GetFontHTM()
{
return "<font color='blue'>"+this.toString()+"</font>";
}
String.prototype.gethtm=GetFontHTM;
</script>
</head>
<body>
<div id="test">
</div>
<script>
var divid=document.getElementById("test");
divid.innerHTML="Test".gethtm();
</script>
</body>
</html>
Another example is shown below
Even though a Car class does not define a property named mileage, we were able to create
one for the mySUV object simply by assigning a value to it. Since we applied this property to
the mySUV object and not the Car class, other objects derived from the Car class will not have
a mileage property
Extend an Existing Object
Just as a class can be extended using the prototype property, objects themselves can have new
properties and methods attached to them.
function Car (make, model, year, color) {
this.Make = make;
this.Model = model;
this.Year = year;
this.Color = color;
this.FullName = this.Year + " " +
"<b>" + this.Make + "</b> " +
this.Model;
}
var mySUV = new Car("Toyota", "4Runner SR5",2001, "Thundercloud");
mySUV.mileage = 12323;
document.write(mySUV.FullName + " has traveled " +mySUV.mileage + " miles.<br><br>");
