Length of a JavaScript object

Question

I have a JavaScript object. Is there a built-in or accepted best practice way to get the length of this object?

const myObject = new Object();
myObject["         


        

Answer 1

To not mess with the prototype or other code, you could build and extend your own object:

function Hash(){
    var length=0;
    this.add = function(key, val){
         if(this[key] == undefined)
         {
           length++;
         }
         this[key]=val;
    }; 
    this.length = function(){
        return length;
    };
}

myArray = new Hash();
myArray.add("lastname", "Simpson");
myArray.add("age", 21);
alert(myArray.length()); // will alert 2

If you always use the add method, the length property will be correct. If you're worried that you or others forget about using it, you could add the property counter which the others have posted to the length method, too.

Of course, you could always overwrite the methods. But even if you do, your code would probably fail noticeably, making it easy to debug. ;)