Question

179

Array length not working

rated 0 times [ 183] [ 4] / answers: 1 / hits: 23000 / 12 Years ago, sat, november 24, 2012, 12:00:00

Possible Duplicate:

Array length undefined

I have the following array but whenever I try to find out the length with categoryData.length it gives me only undefined. If I type console.log(categoryData) it gives me all the objects in the array.

var categoryData = {

animals: {

    name: Animals,

    description: All your favorites from aardvarks to zebras.,

    items: [

        {

            name: Pets

        },

        {

            name: Farm Animals

        },

        {

            name: Wild Animals

        }

    ]

},

colors: {

    name: Colors,

    description: Fresh colors from the magic rainbow.,

    items: [

        {

            name: Blue

        },

        {

            name: Green

        },

        {

            name: Orange

        },

        {

            name: Purple

        },

        {

            name: Red

        },

        {

            name: Yellow

        },

        {

            name: Violet

        }

    ]

},

vehicles: {

    name: Vehicles,

    description: Everything from cars to planes.,

    items: [

        {

            name: Cars

        },

        {

            name: Planes

        },

        {

            name: Construction

        }

    ]

}

};

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sageallenv

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3 Years ago

answered 12 Years ago darennevina · Accepted Answer

That's because categoryData is not an Array - it's an Object. And while some JS objects (arguments, for example) support length property, those created with object literal notation do not.

You can count your object's length by yourself, with this:

function countProps(obj) {

    var count = 0;

    for (var p in obj) {

      obj.hasOwnProperty(p) && count++;

    }

    return count; 

}

This can be done even in a more simple way, if your target environment supports (or has it shimmed) the Object.keys method:

function sizeObj(obj) {

  return Object.keys(obj).length;

}

... and that's exactly how it's done in Underscore.js library method:

_.size = function(obj) {

    if (obj == null) return 0;

    return (obj.length === +obj.length) ? obj.length : _.keys(obj).length;

};