Find a key value in JSON object using a String in JQuery

Question

JSON object as below. Need to find the value based on user input. The input will look like "data.location.type", or "data.location.items[1].address.street". Can it be done in JQuery?

{
    "data": {
        "location": {
            "type": "List",
            "count": 1,
            "items": [
                {
                    "id": 1,
                    "type": "S",
                    "address": {
                        "street": "123 Main St",
                        "city": "New York",
                        "state": "NY"
                    }
                },
                {
                    "id": 2,
                    "type": "S",
                    "address": {
                        "street": "1323 South St",
                        "city": "New York",
                        "state": "NY"
                    }
                }
            ]
        }
    }
}

You don't need jQuery for this, plain JS will do the trick. (And by the way, there's no such thing as a JSON object.) — nnnnnn
– nnnnnn, Commented Oct 17, 2013 at 21:02
@Chris Sure. But, jQuery defines very little for regular Objects, leaving most of that to core ECMAScript and focusing mostly on DOM. The point is just that jQuery isn't much help here. — Jonathan Lonowski
– Jonathan Lonowski, Commented Oct 17, 2013 at 21:07
@Chris: jQuery is NOT a superset of JavaScript. JavaScript is a language. Technically, JavaScript is an implementation and superset of ECMAScript. jQuery is just a code library. It has no language additions. It's an important distinction. — user2736012
– user2736012, Commented Oct 17, 2013 at 21:08
You could not do this in jQuery because it would require you to use javascript's API. The jQuery API does not support this. Where in the jQuery API is the function that says give me an object and a string and I will return a value? If that exists then you can do this with jQuery, and if it does not, then you cannot. It is very straightforward and that is the nature of APIs. Can the API for Math manipulate the DOM? Then no, you cannot manipulate the DOM with Math. — Travis J
– Travis J, Commented Oct 17, 2013 at 21:38
@Chris comes home from the grocery store with a bag of cookies. Chris' wife says, "What's this? I sent you to get sugar, eggs, etc..." Chris replies "Honey, cookies ARE sugar, eggs, etc...". Chris sleeps on the couch that night. — user2736012
– user2736012, Commented Oct 17, 2013 at 21:46

megawac · Accepted Answer · 2013-10-17 21:43:15Z

2

First you're going to need to parse it to an object then use an object lookup function like the one below (here's a fiddle of it in action http://jsfiddle.net/C8zH2/):

//https://gist.github.com/megawac/6162481#file-underscore-lookup-js
var lookup = function(obj, key) {
    var type = typeof key;
    if (type == 'string' || type == "number") key = ("" + key).replace(/\[(.*?)\]/, function(m, key){//handle case where [1] may occur
        return '.' + key;
    }).split('.');
    for (var i = 0, l = key.length, currentkey; i < l; i++) {
        if (obj.hasOwnProperty(key[i])) obj = obj[key[i]];
        else return undefined;
    }
    return obj;
}

//syntax: lookup(jsonobj, input);
//Tests using your data
lookup(data, "data.location.type") //=> "List"
lookup(data, "data.location.items[1].address.street") //=> ""1323 South St"

edited Oct 17, 2013 at 21:43

answered Oct 17, 2013 at 21:05

megawac

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14 Comments

lethal-guitar Over a year ago

How does that lookup function resolve the subscript (items[1])? I don't see that in there, it's just looking for '.'

megawac Over a year ago

Ya I didnt actually handle that case

lethal-guitar Over a year ago

Then you should remove the items.1.address as well, it won't behave as stated in your comment

megawac Over a year ago

@lethal-guitar Yeah I just checked and it will because its calling items["1"]

lethal-guitar Over a year ago

That's right, missed that. Doesn't really help the OP anyway. Another thing: There is an extraneous closing brace here: [i])) It should be just one

|

Tom Bowers · Accepted Answer · 2013-10-17 21:32:57Z

This is just thrown together, but it should work for you...

http://jsfiddle.net/E2hEh/2/

var input = "data.location.type";
//var input = "data.location.items[1].address.street";
var parts = input.split('.');

var prev;
for(var i = 0; i < parts.length; i++){
    var index;
    if(parts[i].indexOf('[') != -1){
        var key = parts[i].substr(0, parts[i].indexOf('['));
        index = parseInt(parts[i].substr(parts[i].indexOf('[') + 1, 1), 10);
        if(!prev){
            prev = test[key][index];
        } else {
            prev = prev[key][index];
        }
    } else { 
        if(!prev){
            prev = test[parts[i]];
        } else {
            prev = prev[parts[i]];
        }

        if(i === parts.length - 1){
            alert(prev);
        }
    }
}

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