For instance, a variable named arrayElements of type array contains:
[{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}].
How do I get the position of the array element with id === 3(3rd element) in the arrayElements variable besides using loop?
thanks.
For instance, a variable named arrayElements of type array contains:
[{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}].
How do I get the position of the array element with id === 3(3rd element) in the arrayElements variable besides using loop?
thanks.
Share Improve this question edited Nov 4, 2014 at 16:05 jcera 3452 silver badges11 bronze badges asked Nov 4, 2014 at 15:21 Julian BergerJulian Berger 1771 silver badge10 bronze badges 06 Answers
Reset to default 7const arrayElements = [
{ id: 1, value: 5 },
{ id: 2, value: 6 },
{ id: 3, value: 7 },
{ id: 4, value: 8 }
]
console.log(arrayElements.findIndex((item) => item.id === 3))
You have to loop at one point. But you can abstract it to look like you're not looping
function indexOfCallback(arr, callback, startIndex) {
if (typeof startIndex == 'undefined') {
startIndex = 0;
}
for(var i=startIndex; i < arr.length; i ++) {
if (callback(arr[i])) {
return i;
}
}
return -1;
}
var array = [{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}];
// Search on id === 3
console.log(indexOfCallback(array, function(obj){
return obj.id === 3;
}));
// Search on value === 6
console.log(indexOfCallback(array, function(obj){
return obj.value === 6;
}));As mentioned by Anthony, this is proposed for ECMAScript 6. Here's the more plete polyfill https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex
if (!Array.prototype.findIndex) {
Array.prototype.findIndex = function(predicate) {
if (this == null) {
throw new TypeError('Array.prototype.find called on null or undefined');
}
if (typeof predicate !== 'function') {
throw new TypeError('predicate must be a function');
}
var list = Object(this);
var length = list.length >>> 0;
var thisArg = arguments[1];
var value;
for (var i = 0; i < length; i++) {
value = list[i];
if (predicate.call(thisArg, value, i, list)) {
return i;
}
}
return -1;
};
}
console.log(array.findIndex(function(obj){
return obj.id === 3;
}));
arrayElements.map(o => o.id).indexOf(3);
Notes:
- Possibly slower than a loop because transforms whole array prior to search. But with high-level languages like Javascript, you never know.
- Infinitely more readable than a loop.
- IE patible (unlike findIndex as of 2017).
In an array like this, you cant access elements by id. So using a loop is the best solution you have. However, depending on your use case you could also consider using an object instead of an array for direct access.
var container = { 1: {id:1, value:5}, 2: {id:2, value:6}, 3: {id:3, value:7} }
You can use an array filter but I think that you will get a better solution using a loop.
var array = [{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}];
var result = array.filter(condition);
function condition(value, index){
if (value.id === 3) return index;
}
console.log(result);
I wrote a function for you that you can use get the job done, but it uses a loop:
var yourObjArray = [{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}];
function objArrayIndex(objArray){
for(var i = 0; i < objArray.length; i++){
if(objArray[i]['id'] == 3){
return i;
}
}
return -1;
}
console.log(objArrayIndex(yourObjArray));