Hi I am trying to print out the first element and the element attached to that element in an array. I am getting 'helloh' in firefox and 'helloundefined' in IE. Does anyone know why this isn't working.
Here is a jsfiddle.. http://jsfiddle.net/ZtuAu/
<script language=javascript>
var test = new Array();
test[0] = new Array();
test[0] = "hello";
test[0][0] = "world";
document.write(test[0] + test[0][0]);
</script>
test[0] can only have one value. You're trying to give it two values. And, you're also finding out that only some browsers allow using array syntax to retrieve particular characters in a string.
First, you do this:
test[0] = new Array();
Then, you do this:
test[0] = "hello";
The second one replaces your first one so that test[0] does not contain an array, it contains a single string "hello" so when do do this:
test[0][0] = "world"
you are trying to assign [0] on a the "hello" string in test[0] which is not allowed by the string object (so it does nothing).
Then, when you try to read test[0][0] in your document.write() statement, you are trying to do [0] on the "hello" string that's in test[0]. Indexing a string with array syntax is not technically allowed by the string object, but some browsers permit it anyway as a shortcut means of retrieving individual characters from a string. That's why you get a different result in different browsers (it returns the 0th character of the "hello" string which is "h").
Note: if you actually want to retrieve a particular character of a string, use charAt(n). See MDN for doc.
Perhaps what you want do do is this:
<script language=javascript>
var test = new Array();
test[0] = "hello";
test[1] = "world";
document.write(test[0] + test[1]);
</script>
You have an array
var test = new Array();
If you want to insert an item into it, use push
test[0] = new Array(); // not this way
test.push(new Array()); // this way
Because you want the array to update its length property etc.
So, you do this:
test[0] = new Array();
test[0] = "hello";
You're assigning the same thing twice, so naturally, only the second assignment holds. So we have
test[0] == "hello"
Then, in FireFox, you can use [] to access any character of the string
test[0][0] == "hello"[0] == "h"
Apparently, in IE you cannot do that, so you get undefined.
You first make test[0][0] an array, and then just put a string into it. So test[0] is hello, and test[0][0] is h as it is the 0th element of the hello string. So you get hello + h
On the third line (test[0] = new Array();), you set test[0] to a new array.
On the next line (test[0] = "hello";), you set it to a string.
Then with test[0][0] = "world"; you try to set that string's first index to "world".
That's like trying to do "hello"[0] = "world";. You can't do that. The String object in JavaScript is immutable.
var test = Array(); makes a 1 dimensional structure... like this:
0 - [_]
1 - [_]
2 - [_]
3 - [_]
4 - [_]
Then, setting the first spot to a new array gives it a second dimension (but only in the first spot).
0 - [_][_][_][_][_]
1 - [_]
2 - [_]
3 - [_]
4 - [_]
Then, setting the first spot to "Hello" gets rid of the array you put there.
0 - ["Hello"]
1 - [_]
2 - [_]
3 - [_]
4 - [_]
At this point, test[0] is "Hello". Not the standard Array that you want it to be. You can't set [0] of a string.
When you ask try to set [0] of a String like "Hello", nothing actually happens, so the line test[0][0] = "world"; isn't really doing anything at all!.
Deep down, Strings are the same as Arrays. Array operations can even be applied to a String. The extent to which browsers expose the underlying similarities isn't really consistent. In FF, Chrome, and Safari, you'll test[0][0] is getting [0] of "Hello". In those browsers, Hello is kinda the same as ["H","e","l","l","o"]. So, test[0][0] = "Hello"[0] = "H". IE doesn't treat strings that way. That's why you're seeing inconsistent behavior.
Hope this helped!
EDIT: As someone else has already suggested, using charAt(x) is the function you should use when trying to pull a character at a specific position from a string.
