Javascript array and loop

Question

I need help trying to get my code to work. I want to be able to loop my arrays and use the if command to make sure the array is there.

arr = ["1","2","3","4"];
for (var i = 0; i < arr.length; i++) {
   if (string != arr[i]) {
  //do something
   }
}

But it does not work. the if command ignores.

    var arr = ["150","-75"];

right = righ + "px";
leftpl=left * 1; 
    if (left < 325){        
leftplu = leftpl + 10; leftplus = leftplu + 'px ';
    for (var i = 0; i < arr.length; i++) {
    if (leftplus+right != arr[i]){
document.getElementById("new").innerHTML=leftplu+'px ' + righ+'px';
        }
    }
    }

or can I put the for loop in the "if (leftplus+right != arr[i])" like "if (leftplus+right != for for (var i = 0; i < arr.length; i++) {arr[i]})"

I apologize, for my poor effort to understand. I'm new to javascript and trying to learn.

What I said is misunderstanding. What I mean, its if the string finds that array, it does something. — Brian
– Brian, Commented Jul 10, 2012 at 1:52
Do you actually have separate variables leftplu, leftpl, and leftplus (if so you should probably come up with different names, if not you have typos) -- also right and righ? — nbrooks
– nbrooks, Commented Jul 10, 2012 at 2:17
lol fair enough. The danger is if it becomes confusing. Right now you do if (leftplus+right != arr[i]) -- but leftplus and right are both strings, so you are essentially saying if ('50px 60px' != "150") (obviously I made up the numbers in front of px but you get the idea) -- so the code in the if should run everytime and keep overwriting the contents of element new. Is that what you see? — nbrooks
– nbrooks, Commented Jul 10, 2012 at 2:30

jeff · Accepted Answer · 2012-07-10 01:58:27Z

2

Change this:

string != arr[i]

To this:

typeof arr[i] != "string"

JavaScript is a loosely typed language and therefore has no keyword string. Instead, as shown above, you can use the typeof operator to obtain the data type of its operand as a string.

With this change, your final code should look like this:

arr = ["1","2","3","4"];
for (var i = 0; i < arr.length; i++) {
   if (typeof arr[i] != "string") {
       //do something
   }
}

edited Jul 10, 2012 at 1:58

answered Jul 10, 2012 at 1:50

jeff

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5 Comments

Brian Over a year ago

Not quite working, but I understand the logic of the your idea. But let me ask, is it possible to create a for loop within a if?

jeff Over a year ago

Yes, it's possible to create a for loop within an if conditional. However, I'm not sure why the posted code is not working. I updated my answer to include the full code. Is this the code you are using?

Brian Over a year ago

Technically, no. This is just something I wrote that looks very similar. I'm confused as well, It should work, but it's not. It's very aggravating.

jeff Over a year ago

Well, I just tested my code. It's working correctly, so it must be something you're doing differently in your real code. Can you please post that code?

jeff Over a year ago

I'm very confused as to what exactly you're trying to do. You're currently adding two strings with the suffix "px" and comparing them to a numeric string. Perhaps this is what you're trying to accomplish: if (parseFloat(leftplus)+parseFloat(right) != parseFloat(arr[i]))

ttt · Accepted Answer · 2012-07-10 05:33:09Z

1

This line: "leftplus+right"

contains strings like "123px456px" it is pointless to compare these with the array values...

I will guess you meant to add numbers together instead of connecting these strings

answered Jul 10, 2012 at 5:33

ttt

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