Compare array variables

Question

when trying to run the following code:

var pvals = new Array();
pvals = "[" + $("#upcheck").val() + "]";
pvals = $.parseJSON(pvals);
pvals = pvals.sort(function(a,b) { return parseFloat(a.id) - parseFloat(b.id) } );

for (var i = 0; pvals.length; i++) {
    if (i == 0) {
       //do something
    } else {
        if (pvals[i].id == pvals[i - 1].id) {
            //do something
        } else {
            //do something else
        }
    }
}

Firebug within Firefox shows the following message "TypeError: pvals[(i - 1)] is undefined" Can anyone please help? I have defined pvals as an array.

Thanks

Ryan

i am getting the json from a textbox, i have updated the code above to what im using and this is the json in the textbox: {"id": "3", "field": "name", "previous": "john"},{"id": "3", "field": "ext", "previous": "1234"},{"id": "2", "field": "name", "previous": "bill"} — rbradshaw
– rbradshaw, Commented May 1, 2014 at 20:06
Please check my the last part of my response. You're running out of bounds when i == 4. — Sunny Patel
– Sunny Patel, Commented May 1, 2014 at 20:10

juvian · Accepted Answer · 2014-05-01 19:55:17Z

1

This should work:

pvals = '[{"id": "3", "field": "name", "previous": "john"},{"id": "3", "field": "ext", "previous": "1234"},{"id": "2", "field": "name", "previous": "bill"}]';

Also:

for (var i = 0; i<pvals.length; i++) { // if not loop doesnt stop

answered May 1, 2014 at 19:55

juvian

16.1k2 gold badges42 silver badges40 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

000 · Accepted Answer · 2014-05-01 19:57:15Z

1

It doesn't make a bit of sense to write json as a string, then immediately parse it.

Rather than using JavaScript Object Notation as a string, just notate the object in javascript.

pvals = [{"id": "3", "field": "name", "previous": "john"},{"id": "3", "field": "ext", "previous": "1234"},{"id": "2", "field": "name", "previous": "bill"}];

answered May 1, 2014 at 19:57

000

27.3k10 gold badges74 silver badges103 bronze badges

Comments

Sunny Patel · Accepted Answer · 2014-05-01 20:07:29Z

0

The way you define pvals doesn't work. You need to escape the quotes.

pvals = '[{"id": "3", "field": "name", "previous": "john"},{"id": "3", "field": "ext", "previous": "1234"},{"id": "2", "field": "name", "previous": "bill"}]';

Alternatively, just use it as an array, and forget the JSON.parse():

pvals = [{"id": "3", "field": "name", "previous": "john"},{"id": "3", "field": "ext", "previous": "1234"},{"id": "2", "field": "name", "previous": "bill"}];

Also, your for loop doesn't end unless pvals.length becomes 0 or false. You should change that line to for (var i = 0; i < pvals.length; i++) {, which will fix your undefined error since you were trying to access an array index that was out of bounds.

Edit: The last statement still holds true based on OP's edited question.

edited May 1, 2014 at 20:07

answered May 1, 2014 at 19:56

Sunny Patel

8,0972 gold badges35 silver badges47 bronze badges

4 Comments

SLaks Over a year ago

No; use an array literal.

Sunny Patel Over a year ago

We're not sure if the data he's actually getting is in the form of JSON, or a JSON string.

000 Over a year ago

What's the difference?

Sunny Patel Over a year ago

Haha, fubar'ed there.. I meant "Javascript Object, or a JSON string". Thanks @JoeFrambach

Collectives™ on Stack Overflow

Compare array variables

3 Answers 3

Comments

Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related