having problems with for loop in javascript

Question

I have a table with numbers but they are stored as string so I am trying to use the function parseFloat to convert it into a table of ints. However, no matter how I do the for loops it gives me a blank table. I can parse the row and it will give me a single int. I can parse a single int as well but cant seem to parse a row or the table. here is what I have so far. This is just trying to convert one row. I tried two for loops for the entire table but that didn't work either. thanks.

 var c =[];
    var entries = $.parseJSON('<?php print(json_encode($try, true)); ?>');  
       for (var j = 0; j < 12; j++)
       {
         for (var i = 0; i < 7; i++)
         { 
         c [j][i] = parseFloat(entries[j][i]);
         }
       }
alert(c);

here is entries json encodes [["-248","-163","-455","-1413","-1294","-1296","-1089"],["-172","-219","-1186","-1368","-1480","-1079","-845"],["-98","-198","-703","-996","-1100","-585","-616"],["-116","-241","-498","-642","-704","-354","-430"],["-137","-117","-264","-525","-533","-269","-476"],["-12","87","-257","-463","-551","-302","-535"],["170","61","-250","-472","-659","-220","-605"],["159","96","-234","-513","-617","-196","-710"],["185","117","-272","-521","-610","-258","-798"],["208","95","-234","-534","-696","-280","-854"],["192","151","-188","-641","-739","-279","-957"],["249","223","-235","-684","-763","-339","-978"]]

it is saying uncaught type error cannot set property 0 to undefined after parseFloat — Austen Novis
– Austen Novis, Commented Mar 2, 2013 at 2:23

jfriend00 · Accepted Answer · 2013-03-02 02:26:04Z

3

You have to initialize the second dimension of your array to also be an array. As it stands now, c[j] is just a single value so you can't do c[j][i] on it. There is also an error in your first for loop where you need to compare the value of j, not i. See this fixed code:

var c = [];
var entries = $.parseJSON('<?php print(json_encode($try, true)); ?>');  
   for (var j = 0; j < 12; j++)
   {
     c[j] = [];
     for (var i = 0; i < 7; i++)
     { 
         c [j][i] = parseFloat(entries[j][i]);
     }
   }
alert(c);

answered Mar 2, 2013 at 2:26

jfriend00

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2 Comments

Austen Novis Over a year ago

yes that would do it. thanks so much. didn't realize I had to do that. makes so much sense now

jfriend00 Over a year ago

@AustenNovis - rather than your hard coded lengths, you could use the .length property of the entries arrays. That would make your code more robust if the data is ever edited and is a better practice in general.

Derek · Accepted Answer · 2013-03-02 02:33:41Z

0

In your first loop for (var j = 0; i < 12; j++), you are using i for iteration but it is undefined and it should be j instead of i

var c =[];
var entries = $.parseJSON('<?php print(json_encode($try, true)); ?>');  
for (var j = 0; j < entries.length ; j++)
{
    c[j] = [];
    for (var i = 0; i < entries[i].length ; i++)
    {          
       c [j][i] = parseFloat(entries[j][i]);
    }
}

edited Mar 2, 2013 at 2:33

answered Mar 2, 2013 at 2:26

Derek

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