How to iterate an array in javascript

Question

I have an array like var arr = { 30,80,20,100 };

And now i want to iterate the above array and add the iterated individual values to one function return statement for example

function iterate()
{
 return "Hours" + arr[i];
}

I had tried in the following approach

function m()
{
 for(var i in arr)
 {
 s = arr[i];
 }
 document.write(s);
}

The above code will gives only one value i.e. last value in an array. But i want to iterate all values like

30---for first Iteration
80---for second Iteraton
Any help will be appreciated

• Felix Kling: In each iteration you are overriding s with arr[i]. Since s can only be one value, what did you expect s to be after the loop?
• Felix Kling: You should also be aware of what document.write is doing after the DOM is loaded: developer.mozilla.org/en/document.write

Answer 1

Iterate over using the length property rather than a for ... in statement and write the array value from inside the loop.

for (var ii = 0, len = arr.length; ii < len; ii++) {
 document.write(arr[ii]);
}

• Jivings: Out of interest, why ii and not just i?
• gen_Eric: @Jivings: Why not? You can name a variable anything.
• Noah Freitas: @Jivings It's an old habit that I picked up from one of my teachers. I think the logic was that ii is easier to find and replace than just i. I don't think I've ever had to use it, but it has become habit at this point.

Answer 2

That's because your write statement is outside the loop. Don't you want it like this?

function m(arr) {
 for (var i = 0; i < arr.length; i++) {
 s = arr[i];
 document.write(s);
 }
}​

Also, don't use in because it will give you ALL the properties of array. Use array.length

• Nithin: Thanks for your reply. The thing is i want to access the array out side of the loop .
• Felix Kling: @Nithin: Then you should have asked your question properly and precisely. But I think you gain more from reading the MDN JavaScript Guide, especially about arrays. You have to at least learn the basics of a language before you can use it.