How can I get the index of an object by its property in JavaScript?

Question

For example, I have:

var Data = [
  { id_list: 1, name: 'Nick', token: '312312' },
  { id_list: 2, name: 'John', token: '123123' },
]

Then, I want to sort/reverse this object by name, for example. And then I want to get something like this:

var Data = [
  { id_list: 2, name: 'John', token: '123123' },
  { id_list: 1, name: 'Nick', token: '312312' },
]

And now I want to know the index of the object with property name='John' to get the value of the property token.

How do I solve the problem?

Answer 1

Since the sort part is already answered. I'm just going to propose another elegant way to get the indexOf of a property in your array

Your example is:

var Data = [     {id_list:1, name:'Nick', token:'312312'},     {id_list:2, name:'John', token:'123123'} ] 

You can do:

var index = Data.map(function(e) { return e.name; }).indexOf('Nick'); 

var Data = [{     id_list: 1,     name: 'Nick',     token: '312312'   },   {     id_list: 2,     name: 'John',     token: '123123'   } ] var index = Data.map(function(e) {   return e.name; }).indexOf('Nick'); console.log(index)

Array.prototype.map is not available on Internet Explorer 7 or Internet Explorer 8. ES5 Compatibility

And here it is with ES6 and arrow syntax, which is even simpler:

const index = Data.map(e => e.name).indexOf('Nick'); 

Answer 2

If you're fine with using ES6, arrays now have the findIndex function. Which means you can do something like this:

const index = Data.findIndex(item => item.name === 'John');

Answer 3

As the other answers suggest, looping through the array is probably the best way. But I would put it in its own function, and make it a little more abstract:

function findWithAttr(array, attr, value) {
    for(var i = 0; i < array.length; i += 1) {
        if(array[i][attr] === value) {
            return i;
        }
    }
    return -1;
}

var Data = [
    {id_list: 2, name: 'John', token: '123123'},
    {id_list: 1, name: 'Nick', token: '312312'}
];

With this, not only can you find which one contains 'John', but you can find which contains the token '312312':

findWithAttr(Data, 'name', 'John'); // returns 0
findWithAttr(Data, 'token', '312312'); // returns 1
findWithAttr(Data, 'id_list', '10'); // returns -1

The function returns -1 when not found, so it follows the same construct as Array.prototype.indexOf().

Answer 4

If you're having issues with Internet Explorer, you could use the map() function which is supported from 9.0 onward:

var index = Data.map(item => item.name).indexOf("Nick");

Answer 5

var index = Data.findIndex(item => item.name == "John")

Which is a simplified version of:

var index = Data.findIndex(function(item){ return item.name == "John"})

From mozilla.org:

The findIndex() method returns the index of the first element in the array that satisfies the provided testing function. Otherwise -1 is returned.

Answer 6

Only way known to me is to loop through all array:

var index = -1;
for(var i=0; i<Data.length; i++)
  if(Data[i].name === "John") {
    index = i;
    break;
  }

Or case insensitive:

var index = -1;
for(var i=0; i<Data.length; i++)
  if(Data[i].name.toLowerCase() === "john") {
    index = i;
    break;
  }

On result variable index contain index of object or -1 if not found.

Answer 7

A prototypical way

(function(){
  if (!Array.prototype.indexOfPropertyValue){
       Array.prototype.indexOfPropertyValue = function(prop, value){
      for (var index = 0; index < this.length; index++){
        if (this[index][prop]){
          if (this[index][prop] == value){
            return index;
          }
        }
       }
      return -1;
    }
  }
 })();

 // Usage:
 var Data = [
   {id_list:1, name:'Nick', token:'312312'}, {id_list:2, name:'John', token:'123123'}];

 Data.indexOfPropertyValue('name', 'John'); // Returns 1 (index of array);
 Data.indexOfPropertyValue('name', 'Invalid name') // Returns -1 (no result);
 var indexOfArray = Data.indexOfPropertyValue('name', 'John');
 Data[indexOfArray] // Returns the desired object.

Answer 8

you can use filter method

 const filteredData = data.filter(e => e.name !== 'john');

Answer 9

Just go through your array and find the position:

var i = 0;
for(var item in Data) {
    if(Data[item].name == 'John')
        break;
    i++;
}
alert(i);

Answer 10

let indexOf = -1;
let theProperty = "value"
let searchFor = "something";

theArray.every(function (element, index) {

    if (element[theProperty] === searchFor) {
        indexOf = index;
        return false;
    }
    return true;
});

Answer 11

collection.findIndex(item => item.value === 'smth') !== -1