How to make a "dot function" in javascript

Question

I'm trying to define a "dot function" where there are no parameters but has a . and a string or number before it like these:

.toUpperCase()
.toLowerCase()
.indexOf()
.charAt()
.substring()

You do 2..toString, not toString(2).

How do you define one of them?

Answer 1

Defining a "dot function" is easy. Here's how you can define it on a single object.

var a = {}, or a = function() {}, or a = [], etc.  a.dotFunction = function() { return 'hi'; }  console.log(a.dotFunction()); 

If you want to define it on all instances of a "class", use prototype.

function someClass() { }  someClass.prototype.dotFunction = function() { return 'hi'; };  console.log(new someClass().dotFunction()); 

You can even do this on built-in types (some, like Prototype.js, do this, though most recommended against it).

Number.prototype.dotFunction = function() { return 'hi'; };  console.log((0).dotFunction());  

Answer 2

I'd strongly recommend not trying to replace any built-in methods, however, you're free to define your own methods however you like.

You can do this by attaching the method to the Number or String type's prototype:

Number.prototype.foo = function(n) { return this * n; }; String.prototype.bar = function(n) { return this.length * n; };  alert(4..foo(2));  // 8 alert("4".bar(2)); // 2 

Further Reading

• Inheritance and the prototype chain