Javascript loop and build array but variable indexed undefined

Question

dont laugh think im having a long day work blonde moment as im a bit out of practice with JS. Any helped appreciated for what I think is a stupidly simple problem.

optionarray = [];

for(i=0;i<response.length;i++) {

    optionarray[i]['content'] = response[i]['name'];
    optionarray[i]['value'] = response[i]['id'];
}

I keep getting optionarray[i] is undefined when trying to add it to the array and build it. I know im doing something ridiculously stupid I just can't remember what :)

Many thanks for any help in advance.

Thank you everyone for your help. I was being dumb :) Thinking too much the PHP way ;) — Jimbo
– Jimbo, Commented Sep 15, 2011 at 20:34

Dmitry · Accepted Answer · 2011-09-15 19:25:50Z

3

optionarray = [];

for(i=0;i<response.length;i++) {

    optionarray[i] = {
            'content' :response[i]['name'], 
            'value': response[i]['id']
    };

}

answered Sep 15, 2011 at 19:25

Dmitry

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Comments

Jon · Accepted Answer · 2011-09-15 19:31:22Z

1

You are trying to access properties of optionarray[i], which does not exist.

What you should be doing in each iteration is

adding a new object to optionarray
setting that object's properties

You can do both at once like this:

optionarray = [];

for(i=0;i<response.length;i++) {
    optionarray.push({
        content: response[i]['name'],
        value: response[i]['id']
    });
}

edited Sep 15, 2011 at 19:31

answered Sep 15, 2011 at 19:23

Jon

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3 Comments

Eric Wendelin Over a year ago

I like this solution better than mine, but I think it's "push" and not "push_back"

Jon Over a year ago

@PhilParsons: Ooops! C++ bug there :) -- fixed.

Phil Parsons Over a year ago

ha, yeah often find myself doing similar. And this is the best approach in my opinion. Although I don't see the point of moving the data from one array to another (perhaps I am missing the bigger picture!)

Eric Wendelin · Accepted Answer · 2011-09-15 19:32:08Z

1

I think you just need to initialize the optionarray[i] object within your for loop:

var optionarray = []; //NOTE: I added var here so because otherwise it's an implicit global

for(i=0;i<response.length;i++) {
    optionarray[i] = {};
    optionarray[i]['content'] = response[i]['name'];
    optionarray[i]['value'] = response[i]['id'];
    // BETTER: optionarray.push({content: response[i]['name'], value: response[i]['id']});
}

if I'm not mistaken.

edited Sep 15, 2011 at 19:32

answered Sep 15, 2011 at 19:24

Eric Wendelin

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1 Comment

Jimbo Over a year ago

Thanks for your help much appreciate ;-)

Gregory Nozik · Accepted Answer · 2011-09-15 19:25:27Z

0

Try this one

optionarray[i] = [];
optionarray[i]['content'] = response[i]['name'];     
optionarray[i]['value'] = response[i]['id'];

You need to define optionarray[i] as array first

answered Sep 15, 2011 at 19:25

Gregory Nozik

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