Unable to initialize JavaScript Class to name keyword

Question

        var NameOne = function (firstName, lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
        }
        NameOne.prototype.getName=function(){
            console.log(this.firstName+' '+this.lastName);
        }
        var name = new NameOne('Prashant','Jain');
        name.getName();

ERROR

Uncaught TypeError: name.getName is not a function

getting above error in browsers if naming object as name and running on browsers. It is working fine on nodejs.

score 3 · Answer 1 · answered Oct 08 '15 at 11:16

window.name is a getter/setter style property in browsers which converts everything to String (to be the name of the Window)

Therefore varing it does not work as you expect and you end up with

name; // "[object Object]"

You will need to either

Choose a different identifier to avoid this conflict
Work in a scope other than the global scope so var will work for name

score 2 · Answer 2 · answered Oct 08 '15 at 11:23

This is because in javascript name is in-built property. so when you call name.getName() it will be actually called on global window object as below window.name.getName() which will throw an error. You need to choose different identifier other than 'name' to work it properly.

score 1 · Answer 3 · edited May 23 '17 at 12:22

In a browser, the global scope refers to the window object, which has a property called name.

If you read about scoping in JavaScript, for example in W3Schools, you'll find this information (at the bottom of the page):

Your global variables (or functions) can overwrite window variables (or functions). Any function, including the window object, can overwrite your global variables and functions.

That means that, if you try to define any variable or function which already exists as a member of the global window object, you will not be able to do it. When you try to access them, you'll be accessing the global window object member.

You can check that, after creating your object name === window.name yields true, which means that it's not your object, but the window.name property.

You can also check that whenever you create a var in the global scope, it's created as a member of window. i.e.

var x = 22;
window.hasOwnProperty('x'); // returns true
console.log(window.x); // you'll see 22 in your console

To get rid of this problem you need to scope your variable. JavaScript only creates new scopes in function's bodies. So, one way to create your own scope it's to use the "self executing anonymous function" pattern, which looks like this:

(function(){ 
   /* new scope: variables are created here without window global object
   *  interference. You can still access globlas using window.globalName */ 
})();

You can read an interesting article on this pattern here.

In node.js there is no name in the global scope, thus you don't have that problem. There is a great explanation of what is in node.js global scope in this great SO answer.

Unable to initialize JavaScript Class to name keyword

3 Answers3