Jquery how to find an Object by attribute in an Array

Question

Given I have an array of \"purpose\" objects:

//array of purpose objects:
var purposeObjects = [
    {purpose: \"daily\"},
    {purpose: \"weekly\"},
    {pu         


        

Answer 1

The error was that you cannot use this in the grep, but you must use a reference to the element. This works:

function findPurpose(purposeName){
    return $.grep(purposeObjects, function(n, i){
      return n.purpose == purposeName;
    });
};

findPurpose("daily");

returns:

[Object { purpose="daily"}]

Answer 2

Best, Fastest way is

function arrayLookup(array, prop, val) {
    for (var i = 0, len = array.length; i < len; i++) {
        if (array[i].hasOwnProperty(prop) && array[i][prop] === val) {
            return array[i];
        }
    }
    return null;
}

Answer 3

I have created a util service for my angular application. It have two function which use very often.

For example you have object.

First getting value from object recursively without throwing undefined error.

{prop: { nestedProp1: {nestedProp2: somevalue}}}; get nestedProp2 2 without undefined checks.

Second filter array on basis

[{prop: { nestedProp1: {nestedProp2: somevalue1}}}, {prop: { nestedProp1: {nestedProp2: somevalue2}}}];

Find object from array with nestedProp2=somevalue2

app.service('UtilService', function(httpService) {
this.mapStringKeyVal = function(map, field) {
    var lastIdentifiedVal = null;
    var parentVal = map;
    field.split('.').forEach(function(val){
        if(parentVal[val]){
            lastIdentifiedVal = parentVal[val]; 
            parentVal = parentVal[val]; 
        }
    });
    return lastIdentifiedVal;
}


this.arrayPropFilter = function(array, field,value) {
    var lastIdentifiedVal = null;
    var mapStringKeyVal = this.mapStringKeyVal;
    array.forEach(function(arrayItem){
        var valueFound = mapStringKeyVal(arrayItem,field);
        if(!lastIdentifiedVal  && valueFound && valueFound==value){
            lastIdentifiedVal = arrayItem;
        }
    });
    return lastIdentifiedVal;
}});

For solution for current question. inject UtilService and call,

UtilService.arrayPropFilter(purposeArray,'purpose','daily');

Or more advanced

UtilService.arrayPropFilter(purposeArray,'purpose.nestedProp1.nestedProp2','daily');

Answer 4

I personally use a more generic function that works for any property of any array:

function lookup(array, prop, value) {
    for (var i = 0, len = array.length; i < len; i++)
        if (array[i] && array[i][prop] === value) return array[i];
}

You just call it like this:

lookup(purposeObjects, "purpose", "daily");

Answer 5

One more solution:

function firstOrNull(array, expr) {
  for (var i = 0; i < array.length; i++) {
    if (expr(array[i]))
      return array[i];
    }
  return null;
}

Using: firstOrNull([{ a: 1, b: 2 }, { a: 3, b: 3 }], function(item) { return item.a === 3; });

This function don't executes for each element from the array (it's valuable for large arrays)