js data prototype attribute_basic knowledge

Information: prototype attribute
Returns a reference to the prototype of the object type.
objectName.prototype
objectName parameter is the name of the object.

Description
Use the prototype attribute to provide a set of basic functions of the object's class. New instances of an object "inherit" the operations assigned to the object's prototype.

For example, add a method to the Array object that returns the value of the largest element in the array. To accomplish this, declare the function, add it to Array.prototype, and use it.

Copy code The code is as follows:

function array_max( ){
var i, max = this[0];
for (i = 1; i < this.length; i )
{
if (max < this[i])
max = this[i] ;
}
return max;
}
Array.prototype.max = array_max;
var x = new Array(1, 2, 3, 4, 5, 6);
var y = x.max( );

After this code is executed, y saves the maximum value in the array x, or 6.

All JScript internal objects have a read-only prototype attribute. You can add functionality to a prototype as in this example, but the object cannot be assigned a different prototype. However, user-defined objects can be assigned to new prototypes.

The list of methods and properties for each internal object in this language reference indicates which ones are part of the object's prototype and which ones are not.