evaluate variable as part of JSON query

Question

I've got this:

var JSON = [
    {
        "id": 1,
        "name1": "Seymore Butts",
        "name2": "Jane Doe",
        "name3": "John Smith",
        "name4": "Mike Hawk"
    }];
for (i = 1; i < 5; i++) {
    var index = "name" + i;
    window.console.log(JSON[0].index);
}

and of course it's getting undefined because it's looking for

JSON[0].index

instead of

JSON[0].name1

Any way to force it to evaluate the index var instead of just reading "index"?

For future reference, you have an array of *javascript objects*, not *JSON* (which is always, by definition, a string) — jbabey, Aug 02 '13 at 17:43
possible duplicate of [JavaScript object: access variable property by name as string](http://stackoverflow.com/questions/4255472/javascript-object-access-variable-property-by-name-as-string), http://stackoverflow.com/questions/3153969/create-object-using-variables-for-property-name, http://stackoverflow.com/questions/2241875/how-to-create-object-property-from-variable-value-in-javascript, http://stackoverflow.com/questions/4694652/javascript-creating-object-and-using-variable-for-property-name, etc... — jbabey, Aug 02 '13 at 17:44

score 4 · Accepted Answer · answered Aug 02 '13 at 17:44

4

Yup, just change your syntax to:

window.console.log(JSON[0][index]);

answered Aug 02 '13 at 17:44

Kyle Fransham

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score 2 · Answer 2 · answered Aug 02 '13 at 17:44

Use this:

for (i = 1; i < 5; i++) {
    var index = "name" + i;
    window.console.log(JSON[0][index]);
}

The difference between . and [] here is that object.sub_field will try to access field named sub_field, while object[sub_field] will try to access field named by "whatever is in variable sub_field".

evaluate variable as part of JSON query

2 Answers2