How to count the number of arrays nested within a JavaScript object by name

Question

I have a generic function that needs to check the number of items in the array that is named, but I don't always know what the name is going to be called. Is there a way to do this?

array:

// added array example here per request:
var myArray = { "name": "myname", "data": [ "item1": [1], "item2": [2,3,4,5,6,7,8,9], "item3": [41,42,51,491]}

// where length is the number of objects in the array.
var mycount = someitem.getProperty("UnknownName").length;

what I want to do is call some function that does this:

var mycount = specialCountFunction(someitem, name);

Please show an simple example of the structure of your object, so that we can help you better. — Paul
– Paul, Commented Feb 22, 2014 at 2:41
This question is incomplete without showing us an example of the data you are searching through and a boilerplate/description of a function you want written (e.g. what info you're going to pass it and what info you want it to return). — jfriend00
– jfriend00, Commented Feb 22, 2014 at 3:15

cookie monster · Accepted Answer · 2014-02-22 02:52:02Z

1

In your specialCountFunction(), receive the property name as a string, and then use square brackets after item to evaluate the value of the string in order to use it as a property name.

function specialCountFunction(item, name) {
    return item[name].length;
}

So then you'd call it like this:

var name = "whatever_the_name_is";
var count = specialCountFunction(someitem, name);

answered Feb 22, 2014 at 2:52

cookie monster

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Comments

Faiz Shukri · Accepted Answer · 2014-02-22 02:54:45Z

1

Do you mean to get the length of an array in an object?

For example, your object

var obj = {
    "children": [ "john", "mark", "sam" ]
}

Get the length with obj["children"].length

Or the length of an object ?

Object.size = function(obj) {
    var size = 0, key;
    for (key in obj) {
        if (obj.hasOwnProperty(key)) size++;
    }
    return size;
};

// Get the size of an object
var size = Object.size(obj);

edited Feb 22, 2014 at 2:54

answered Feb 22, 2014 at 2:48

Faiz Shukri

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2 Comments

user3250966 Over a year ago

Yes. That is precisely what I mean. It is the same thing but its in the rows object in an ng-grid. Each cell can have an array based on the field name and I need to count the number of arrays in the field children.

jfriend00 Over a year ago

@user3250966 - Please use the "edit" button in your question to paste in an example of the actual data you're searching.

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