Javascript loop and build array but variable indexed undefined - Stack Overflow

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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.

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.

• javascript
• arrays
• loops
• undefined

Share Improve this question Follow asked Sep 15, 2011 at 19:21 JimboJimbo 13722 silver badges1111 bronze badges 1

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

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4 Answers 4

Sorted by: Reset to default 3

optionarray = [];

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

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

}

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

What you should be doing in each iteration is

1. adding a new object to optionarray
2. 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']
    });
}

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.

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

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