What's the best way to extract the total number of arrays stored within an object?

Question

What's the best way to extract the total number of arrays stored within an object?

I am working with a JSON webservice that has a specific format.

 { Name:['a','b'], Name:['cd','ef'], Age:{...}, Address:{...} }.

Within this object, there are 2 arrays & 2 objects, though the number of arrays and objects can vary. I am looking for a way to specifically count only the number of arrays within the main object. While there may be other solutions to my issue, I specifically need my code to be implemented in a .JS (JavaScript) file.

Initially, I attempted:

Object.keys(mainobject).length;

However, this approach provided me with a total count of both arrays and objects in the main object.

javascript arrays json object

Answer 1

Answer №1

let info = { Name:['a','b'], OtherName:['cd','ef'], Age:{a: 12}, Address:{a: 'asdf'} }

let numOfArrays = Object.keys(info).filter(function(key) {
    return info[key] instanceof Array; //or Array.isArray(info[key]) if the array was created in another frame
}).length;

alert(numOfArrays);

Please note that this may not be supported in older versions of IE

Check out on jsFiddle

To ensure compatibility with browsers that do not support it, consider using shims from MDN:

Object.keys

Array.filter

Answer 2

let info = { Name:['a','b'], OtherName:['cd','ef'], Age:{a: 12}, Address:{a: 'asdf'} }

let numOfArrays = Object.keys(info).filter(function(key) {
    return info[key] instanceof Array; //or Array.isArray(info[key]) if the array was created in another frame
}).length;

alert(numOfArrays);

Please note that this may not be supported in older versions of IE

Check out on jsFiddle

To ensure compatibility with browsers that do not support it, consider using shims from MDN:

Object.keys

Array.filter

Answer 3

Answer №2

I will create a function to tally up the different data types

var obj = {
    key1: ['a','b'], key2: ['cd','ef'],
    key3: 0, key4: 1,
    key5: {alpha:'beta'},
    key6: new Date(),
    key7: "bar"
};

function checkType(obj) {
    var type = Object.prototype.toString.call(obj).slice(8, -1);
    if (type === 'Object') return obj.constructor.name;
    return type;
}

function countDataTypes(obj) {
    var key, hasOwnProperty = Object.prototype.hasOwnProperty,
        result = {}, dataType;
    for (key in obj) if (hasOwnProperty.call(obj, key)) {
        dataType = checkType(obj[key]);
        if (!result[dataType]) result[dataType] = 1;
        else ++result[dataType];
    }
    return result;
}

var dataTypesCount = countDataTypes(obj);
// Object {Array: 2, Number: 2, Object: 1, Date: 1, String: 1}

If I am interested in knowing just the number of Arrays

var numOfArrays = dataTypesCount.Array || 0; // 2 Arrays in this scenario

Answer 4

I will create a function to tally up the different data types

var obj = {
    key1: ['a','b'], key2: ['cd','ef'],
    key3: 0, key4: 1,
    key5: {alpha:'beta'},
    key6: new Date(),
    key7: "bar"
};

function checkType(obj) {
    var type = Object.prototype.toString.call(obj).slice(8, -1);
    if (type === 'Object') return obj.constructor.name;
    return type;
}

function countDataTypes(obj) {
    var key, hasOwnProperty = Object.prototype.hasOwnProperty,
        result = {}, dataType;
    for (key in obj) if (hasOwnProperty.call(obj, key)) {
        dataType = checkType(obj[key]);
        if (!result[dataType]) result[dataType] = 1;
        else ++result[dataType];
    }
    return result;
}

var dataTypesCount = countDataTypes(obj);
// Object {Array: 2, Number: 2, Object: 1, Date: 1, String: 1}

If I am interested in knowing just the number of Arrays

var numOfArrays = dataTypesCount.Array || 0; // 2 Arrays in this scenario

Answer 5

Answer №3

To determine the type of each item within your object, you could iterate through each member.

var count = 0;
for (var foo in mainobject) {
    if (foo instanceof Array) count++;
}

After running this code, simply access the value stored in count.

Answer 6

To determine the type of each item within your object, you could iterate through each member.

var count = 0;
for (var foo in mainobject) {
    if (foo instanceof Array) count++;
}

After running this code, simply access the value stored in count.

What's the best way to extract the total number of arrays stored within an object?

Answer №1

Answer №2

Answer №3

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