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Returns a reference to the prototype for a date.




For example, to add a method to the Date object that returns the value of the largest element of the array, declare the function, add it to Date.prototype , and then use it.

function max( ){
     var max = new Date();
     max.setFullYear(2200, 01, 01);
     return max;
 Date.prototype.maxDate = max;
 var myDate = new Date();

 if (myDate < myDate.maxDate())
     document.write("today isn't the max");
 else if (myDate == myDate.maxDate())
     document.write("today is the max");

 // Output:
 // today isn't the max


The date argument is the name of an object.

Use the prototype property to provide a base set of functionality to a Date. New instances of an object “inherit” the behavior of the prototype assigned to that object.

All intrinsic JavaScript objects have a prototype property that is read-only. Properties and methods may be added to the prototype, but the object may not be assigned a different prototype. However, user-defined objects may be assigned a new prototype.


  • Microsoft Developer Network: Article