read an array dynamically using getElementById

Question

I am trying to read values from a form dynamically created by user and insert them in an 2 dimensional array. The ID of any field is created dynamically and it has the value 11, 12, 13 etc, depending on the rows and cols of the table. I try to read it using getElementByID but it seems to not work. The function is as follows:

            function readMatrix () {
        for (i = 0; i < k; i++) {
            for (j = 0; j < k; j++)
            A[i][j]=parseFloat(getElementById(ij).value, 10);
        }
    }

You are leaking globals i and j. Use var to avoid this!! And parseFloat does not have a 2nd base argument. Unless you are using HTML5 you also cannot have an ID starting with a number. — ThiefMaster
– ThiefMaster, Commented May 13, 2012 at 19:14
my bad to the below comments. it works perfectly, i made a mistake some place else in the script — viktor
– viktor, Commented May 13, 2012 at 19:41
You firebug (if you are not using it) Highly recommended. getfirebug.com/ — Jashwant
– Jashwant, Commented May 13, 2012 at 19:53

Niet the Dark Absol · Accepted Answer · 2012-05-13 19:12:26Z

2

First, it's document.getElementById(...) - that part is important, otherwise it can't find the getElementById function.

Next, you're having it look for a variable called ij, which is not what you want. You want the two numbers concatenated, so that can either be i*10+j or ""+i+j, whichever you prefer.

answered May 13, 2012 at 19:12

Niet the Dark Absol

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2 Comments

Niet the Dark Absol Over a year ago

It does work, you're just doing something else wrong. Please show your updated code.

viktor Over a year ago

yes you are right I was doing something else wrong. Thank you

Jashwant · Accepted Answer · 2012-05-13 19:14:21Z

1

I guess, elements id is concantenation of i and j , rather than addition.

So, it should work,

   function readMatrix () {
        for (i = 0; i < k; i++) {
            for (j = 0; j < k; j++)
            A[i][j]=parseFloat(document.getElementById(i + '' + j).value, 10);
        }
    }

answered May 13, 2012 at 19:14

Jashwant

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2 Comments

Jashwant Over a year ago

You are trying to get value of which html element ?

Jashwant Over a year ago

Mark question as answer that helps you :)

VisioN · Accepted Answer · 2012-05-13 19:37:12Z

1

You have a problem with getElementById call and argument. Try this:

function readMatrix() {
    for (var i = 0; i < k; i++) {
        for (var j = 0; j < k; j++) {
            var id = "" + (i + 1) + (j + 1);
            A[i][j] = parseFloat(document.getElementById(id).value);
        }
    }
}

Pay attention you have IDs starting from 11 but not 00, so (i + 1) + (j + 1) part is added.

DEMO: http://jsfiddle.net/VnvM2/

edited May 13, 2012 at 19:37

answered May 13, 2012 at 19:13

VisioN

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1 Comment

viktor Over a year ago

the +1 part seems legit, however the function is not working in this form, nor with "A"+(i+1)+(j+1)

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