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.
const 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))
arrayElements.map(o => o.id).indexOf(3);
Notes:
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 complete polyfill https://developer.mozilla.org/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;
}));
findIndex(), which seems to be much the same thing. For now definitely want to implement something like this for yourself, but perhaps at some point there won't be a need to.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));
indexOf, it lets you search an array by specifying what to find as a parameter, but in this case you can't just pass an object that is like it, because they won't pass the equal test. The solution is to let the caller implement the equality function as a callback. Again, see my answer.