Sunday, March 13, 2011

JavaScript Looping Through Object Properties

Looping Through JSON Object Properties in JavaScript.

My previous post contained a small piece of code explaining how to loop through object properties with the Reflection namespace in C#.

In this post I'd like to explain how do loop through JavaScript object.

Let's create an object in JavaScript:

var myObject = {
    Name: "Elad",
    LastName: "Shalom",
    Age: 26,
    Kids: ["Daniel"]
};

This object contains 4 properties:
  1. Name (string)
  2. LastName (string)
  3. Age (int)
  4. Kids (array)
Now  for the loop part:

function LoopThroughProperties(obj)
{
    for (var propName in obj)
    {
        alert(propName + ": " + obj[propName]);
    }
}

The function will receive an object and loop through all of it's properties.

I'd like to take 2-4 more lines to explain a bit about the for syntax I used.
Those of you who write in C# / VB / Java will find it very similar to foreach loop in JavaScript.

Since an object in JavaScript is a form of array, I can easily call every one of it's properties the same way (almost) I'd call them when looping through array.
This type of forach loop in JavaScript is also very useful when going through a hash table.  since we don't know the numbers the hash contains, we can simply loop through it.

Thanks,
Elad Shalom,
CTO at ITweetLive.com

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