As I said earlier, objects are hash tables of properties and functions so looping throught them is done the same way (weepee!).

The “in” statement

The in statement must be used in a for loop. Like this : for (var element in allElements). In most of the other languages, the element variable would contain the complete element but in javascript, it contains the name that refers to the complete element.

Looping through a hash table

Before doing it, maybe you should take a look at How to use javascript hashes (or hash-table) to make sure you fully understand what are javascript hash tables.


// I create a hash table var hashPetNames = new Object();

// I create the pets hashPetNames[“cat”] = “Mistigri”; hashPetNames[“dog”] = “Rex”; hashPetNames[“bird”] = “Bibi”;

// I loop using the “in” statement for (var name in hashPetNames) { alert(“My ” + name + “'s name is ” + hashPetNames[name]); }


Run this code and you should see the alerts : - My cat's name is Mistigri. - My dog's name is Rex. - My bird's name is Bibi.

So easy.

Looping through an object

This one is a little kinkier. Why would I want to loop through an object properties and methods? I can't give you an answer. It's up to you to find it. I've used it a couple of times so it's not as useless as you could think.

Example, I would like to separatly alert all the properties and methods of an object.


// Create the class function TheClass() { = “The class”; this.fullName = “The full name of the class”; this.age = “51”; }

// Add a function TheClass.prototype.alertClass = function() { alert( + “ ” + this.fullName + this.Age); }

// Construct the object var theObject = new TheClass();

// Loop through the properties/functions var properties = “”; for (var propertyName in theObject) { // Check if it's NOT a function if (!(theObject[propertyName] instanceof Function)) { properties += propertyName + “, ”; } }

alert(“Properties : ” + properties);

// Loop through the properties/functions var functions = “”; for (var functionName in theObject) { // Check if it's a function if (theObject[functionName] instanceof Function) { functions += functionName + “, ”; } }

alert(“Functions : ” + functions);