Is there any function in jQuery that is equivalent to PHP's array_column()?

Question

What is the equivalent to PHP\'s array_column() in jQuery? I need the data inside the array without looping, in the same way as in PHP.

Answer 1

At the bottom of this post is my JavaScript implementation of PHP's array_column(). No jQuery needed.

Example usage:

var records = [
    {id: 2135, first_name: 'John',  last_name: 'Doe'},
    {id: 3245, first_name: 'Sally', last_name: 'Smith'},
    {id: 5342, first_name: 'Jane',  last_name: 'Jones'},
    {id: 5623, first_name: 'Peter', last_name: 'Doe'}
];
var first_names = arrayColumn(records, 'first_name');
// => ["John", "Sally", "Jane", "Peter"]
var last_names = arrayColumn(records, 'last_name', 'id');
// => {2135: "Doe", 3245: "Smith", 5342: "Jones", 5623: "Doe"}
var persons = arrayColumn(records, null, 'id');
// => {
//        2135: {id: 2135, first_name: 'John',  last_name: 'Doe'},
//        3245: {id: 3245, first_name: 'Sally', last_name: 'Smith'},
//        5342: {id: 5342, first_name: 'Jane',  last_name: 'Jones'},
//        5623: {id: 5623, first_name: 'Peter', last_name: 'Doe'}
//    }

Implementation:

/**
 * Source: http://stackoverflow.com/a/33841999/1402846
 *
 * This function is (almost) equivalent to array_column() in PHP (http://php.net/manual/function.array-column.php).
 *
 * Differences between this function and PHP's array_column():
 * 

 *     
If indexKey is not found in an element of the input array, the behaviour of this function is undefined.
 *     In PHP's array_column(), the element will be put into the end of the array. It is possible in PHP because PHP does not
 *     distinguish between arrays and dictionaries, but it is not possible in JavaScript because Arrays and Objects are different.
 *
 *     
Associative arrays (dictionaries) in PHP are ordered, JavaScript objects are not (http://stackoverflow.com/a/5525820/14028460.
 *     Do not make assumptions on the ordering of the keys in JavaScript objects.
 *
 *     
If the value of an element at inputKey is not a string, the result of this function and the PHP function
 *     doesn't make much sense. For example, in PHP,
 *     
 *          $records = array(
 *              array('id' => true, 'last_name' => 'Doe')
 *          );
 *          array_column($records, 'last_name', 'id');
 *     
 *     gives Array([1] => Doe), or maybe Array([0] => Doe) due to a bug ({@link https://bugs.php.net/bug.php?id=68553}). But, in JavaScript,
 *     
 *          var records = [
 *              {id: true, last_name: 'Doe'},
 *          ];
 *          arrayColumn(records, 'last_name', 'id');
 *     
 *     gives {true: "Doe"}. Therefore, it is strongly advised to make sure that the value at indexKey of
 *     each input element is a string.
 * 
 *
 * @param {Array|Object} inputArray             The input array, it must either contain objects only or arrays only.
 *                                              If it is an object instead of an array, it would be converted to an array first.
 * @param {int|string|null} columnKey           If the input array contains objects, this parameter is the key in each object.
 *                                              If the input array contains arrays, this parameter is the index in each array.
 *                                              If the key or index is not valid, this element is skipped.
 *                                              This parameter may also be null.
 * @param {int|string|null} [indexKey=null]     If the input array contains objects, this parameter must be a valid key in each object.
 *                                              If the input array contains arrays, this parameter must be a valid index in each array.
 *                                              If it is not a valid key or index, the behaviour is undefined.
 *                                              This parameter may also be null.
 * @returns {Array|Object}                      If indexKey is null, this function returns an array which is parallel
 *                                              to the input array. For each element elem in the input array, the element in the
 *                                              output array would be elem[columnKey], or just elem if columnKey
 *                                              is null.
 *                                              If indexKey is not null, this function returns an object.
 *                                              For each element elem in the input array, the output object would contain an
 *                                              element elem[columnKey], or just elem if columnKey
 *                                              is null, at the key elem[indexKey]. If the value of elem[indexKey]
 *                                              of some elements in the input array are duplicated, the element in the return object would
 *                                              correspond to the element nearest to the end of the input array.
 * @example
 * var records = [
 *      {id: 2135, first_name: 'John',  last_name: 'Doe'},
 *      {id: 3245, first_name: 'Sally', last_name: 'Smith'},
 *      {id: 5342, first_name: 'Jane',  last_name: 'Jones'},
 *      {id: 5623, first_name: 'Peter', last_name: 'Doe'}
 * ];
 * var first_names = arrayColumn(records, 'first_name');
 * >> ["John", "Sally", "Jane", "Peter"]
 * var last_names = arrayColumn(records, 'last_name', 'id');
 * >> {2135: "Doe", 3245: "Smith", 5342: "Jones", 5623: "Doe"}
 * var persons = arrayColumn(records, null, 'id');
 * >> {
 *      2135: {id: 2135, first_name: 'John',  last_name: 'Doe'},
 *      3245: {id: 3245, first_name: 'Sally', last_name: 'Smith'},
 *      5342: {id: 5342, first_name: 'Jane',  last_name: 'Jones'},
 *      5623: {id: 5623, first_name: 'Peter', last_name: 'Doe'}
 *    }
 */
function arrayColumn(inputArray, columnKey, indexKey)
{
    function isArray(inputValue)
    {
        return Object.prototype.toString.call(inputValue) === '[object Array]';
    }

    // If input array is an object instead of an array,
    // convert it to an array.
    if(!isArray(inputArray))
    {
        var newArray = [];
        for(var key in inputArray)
        {
            if(!inputArray.hasOwnProperty(key))
            {
                continue;
            }
            newArray.push(inputArray[key]);
        }
        inputArray = newArray;
    }

    // Process the input array.
    var isReturnArray = (typeof indexKey === 'undefined' || indexKey === null);
    var outputArray = [];
    var outputObject = {};
    for(var inputIndex = 0; inputIndex < inputArray.length; inputIndex++)
    {
        var inputElement = inputArray[inputIndex];

        var outputElement;
        if(columnKey === null)
        {
            outputElement = inputElement;
        }
        else
        {
            if(isArray(inputElement))
            {
                if(columnKey < 0 || columnKey >= inputElement.length)
                {
                    continue;
                }
            }
            else
            {
                if(!inputElement.hasOwnProperty(columnKey))
                {
                    continue;
                }
            }

            outputElement = inputElement[columnKey];
        }

        if(isReturnArray)
        {
            outputArray.push(outputElement);
        }
        else
        {
            outputObject[inputElement[indexKey]] = outputElement;
        }
    }

    return (isReturnArray ? outputArray : outputObject);
}