Question

Possible Duplicate:
Find object by id in array of javascript objects

So I have this:

mapArray=
[{"Title":"crop_rotation","subs":"5,6,7,10"},
{"Title":"cover_crops","subs":"2,5,7,8,9,13,14"},
{"Title":"binary_wetlands","subs":"1,2,3,4,5,6,7,8,9,10,11"}]

I am trying to access the subs value based on the Title. I am trying

listofSubs=mapArray["crop_rotation"]("subs");

I don’t get anything returned. What am I missing here? I need to take that list and convert to a string but I assume it will come out as a string since I have the object already parsed? Thanks in advance

Answer 1

First you have to find the object with the specific title. You have to do this by iterating over the array and comparing each object’s Title against your value:

function find(arr, key, value) {
    for(var i = 0, l = arr.length; i < l; i++) {
        if(arr[i][key] === value)) {
            return arr[i];
        }
    }
    // return {}; // if you would want it null-safe
}

Then you can access the corresponding subs property:

var obj = find(mapArray, 'Title', 'crop_rotation');
if(obj) {
    var listofSubs = obj.subs;
}

---

An explanation for why your code does not work:

mapArray["crop_rotation"]("subs");
//      |-      1      -|-   2  -|

• |1| tries to access the property crop_rotation of the object in mapArray. Arrays don’t have such properties and in your case no object does. crop_rotation is the value of one of the properties.
• |2| is a function call. It tries to call the function referenced by mapArray["crop_rotation"] and passes "subs" as first argument. It throws an error if mapArray["crop_rotation"] is not a function (like in your case).

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Further information:

• MDN JavaScript Guide # Arrays
• MDN JavaScript Guide # Working with Object
• Access / process (nested) objects, arrays or JSON