Differences in function declarations in a Javascript constructor function

I'm confused about the different ways to declare functions inside a constructor function.

function ClassName() {
 this.one = function() {};
 var two = function() {};  
 three = function()开发者_JS百科 {};
}

I know one is public and can be called by the outside and two is private. What are the semantics for three?

The example as you have provided would be a syntax error, as you need to use = for assignment in that context.

three if used with the correct assignment operator would be a global function that would exist outside of that scope. When you omit the var keyword, the variable is assigned a property of the global object, which is window in a browser.

jsFiddle.

When using var, they become properties of the VariableObject in the execution context. You use them as normal variables.

Further Reading.

These are the ones that you can use in a constructor function:

function ClassName() {

  // A function assigned to a property
  this.one = function() {};

  // A function assigned to a local variable
  var two = function() {};

  // A function declared locally
  function three() {}

}

Only the first one ends up as a member of the object.

These are the ones that you can use in an object literal:

var objectName = {

  // A function assigned to a property
  one: function() {}

};

This is the first format

this is closeer to the static methods in other programming languages.

var ClassName = {  
    one: function() {},
    two: function() {},
    three: function() {} 
} 

ex:

  ClassName.one();

and the other is:

function ClassName(){  
    this.one = function() {};
    this.two = function() {};
    this.three = function() {}; 
} 

here you can do:

var obj = new ClassName();
obj.one();

In this case you need to instantiate the object before using the methods.

These are the two ways for classes in javascript... that i know of.