Get property of object in JavaScript

Question

Basically I have a form with a <select> that chooses which set of data to use (values are "m", "f" and "c"). I then have a dictionary/object with the data in:

var gdas = {
    // Male
    "m": {
        "calories": 2500,
        "protein": 55,
        "carbohydrates": 300,
        "sugars": 120,
        "fat": 95,
        "saturates": 30,
        "fibre": 24,
        "salt": 6
    },

    // Female
    "f": {
        "calories": 2000,
        // etc.
};

Now I need to get gdas.m/gdas.f/gdas.c but I'm not sure what syntax to use - I've tried:

var mode = $("#mode").val();
var gda_set = gdas.mode;
var gda_set = gdas[mode];

What's the right syntax/method for this?

possible duplicate of Assigning property to JS object using another objects property value as the property name — Pekka
– Pekka, Commented Sep 12, 2010 at 14:52

user113716 · Accepted Answer · 2010-09-12 14:54:14Z

21

Since you're referencing the property via a variable, you need the bracket notation.

var gda_set = gdas[mode];

...which is the same notation you would use if you were passing a String.

var gda_set = gdas["f"];

answered Sep 12, 2010 at 14:54

user113716

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2 Comments

Ross Over a year ago

You're right, I'm a bit confused as to why it didn't work the first time, probably had my break point in the wrong place. Thanks!

user113716 Over a year ago

@Ross - You're welcome. :o) A fairly common mistake is to place a . before the opening bracket, as in gdas.[mode]. Anyway, glad you got it working!

Tomasz Kowalczyk · Accepted Answer · 2010-09-12 14:52:57Z

2

You don't have "mode" attribute in that variable. You must use if's to detect which sex you are processing and get gdas.m.fibre or gdas.f.salt.

answered Sep 12, 2010 at 14:52

Tomasz Kowalczyk

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1 Comment

Pekka Over a year ago

That's not really his question, is it? He needs to find out how he can make the .m. and .f. dynamic depending on the selected value

halfdan · Accepted Answer · 2010-09-12 14:55:01Z

0

You can use gdas[mode], it selects the element that is indexed by the value of mode.

answered Sep 12, 2010 at 14:55

halfdan

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