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

Use a small workaround:

Create a new array with names as indexes. After that all searches will use indexes. So, only one loop. After that you don't need to loop through all elements!

var Data = [
    {id_list:1, name:'Nick',token:'312312'},{id_list:2,name:'John',token:'123123'}
    ]
var searchArr = []
Data.forEach(function(one){
  searchArr[one.name]=one;
})
console.log(searchArr['Nick'])

http://jsbin.com/xibala/1/edit

Live example.

Answer 10

I extended Chris Pickett's answer, because in my case I needed to search deeper than one attribute level:

function findWithAttr(array, attr, value) {
  if (attr.indexOf('.') >= 0) {
    var split = attr.split('.');
    var attr1 = split[0];
    var attr2 = split[1];
    for(var i = 0; i < array.length; i += 1) {
      if(array[i][attr1][attr2] === value) {
        return i;
      }
    }
  } else {
    for(var i = 0; i < array.length; i += 1) {
      if(array[i][attr] === value) {
        return i;
      }
    }
  };
};

You can pass 'attr1.attr2' into the function.

Answer 11

Use this:

Data.indexOf(_.find(Data, function(element) {
  return element.name === 'John';
}));

It is assuming you are using Lodash or Underscore.js.

Answer 12

var fields = {
  teste:
  {
    Acess:
    {
      Edit: true,
      View: false
    }
  },
  teste1:
  {
    Acess:
    {
      Edit: false,
      View: false
    }
  }
};

console.log(find(fields,'teste'));

function find(fields,field) {
  for(key in fields) {
    if(key == field) {
      return true;
    }
  }
  return false;
}

If you have one Object with multiple objects inside, if you want know if some object are include on Master object, just use find(MasterObject, 'Object to Search'). This function will return the response if it exists or not (TRUE or FALSE). I hope to help with this - can see the example on JSFiddle.

Answer 13

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 14

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

Answer 15

If you want to get the value of the property token then you can also try this:

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

    let resultingToken =  data[_.findKey(data,['name','John'])].token

where _.findKey is a Lodash function.

Answer 16

You can use findIndex in Lodash library.

Example:

var users = [
{ 'user': 'barney',  'active': false },
{ 'user': 'fred',    'active': false },
{ 'user': 'pebbles', 'active': true }
            ];

_.findIndex(users, function(o) { return o.user == 'barney'; });
// => 0

// The `_.matches` iteratee shorthand.
_.findIndex(users, { 'user': 'fred', 'active': false });
// => 1

// The `_.matchesProperty` iteratee shorthand.
_.findIndex(users, ['active', false]);
// => 0

// The `_.property` iteratee shorthand.
_.findIndex(users, 'active');
// => 2

Answer 17

You can use Array.sort using a custom function as a parameter to define your sorting mechanism.

In your example, it would give:

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

Data.sort(function(a, b){
    return a.name < b.name ? -1 : a.name > b.name ? 1 : 0;
});

alert("First name is : " + Data[0].name); // alerts 'John'
alert("Second name is : " + Data[1].name); // alerts 'Nick'

The sort function must return either -1 if a should come before b, 1 if a should come after b and 0 if both are equal. It's up to you to define the right logic in your sorting function to sort the array.

Missed the last part of your question where you want to know the index. You would have to loop through the array to find that as others have said.

Answer 18

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 19

This might be useful:

function showProps(obj, objName) {
  var result = "";
  for (var i in obj)
    result += objName + "." + i + " = " + obj[i] + "\n";
  return result;
}

I copied this from Working with objects.

Answer 20

Alternatively to German Attanasio Ruiz's answer, you can eliminate the second loop by using Array.reduce() instead of Array.map();

var Data = [
    { name: 'hypno7oad' }
]
var indexOfTarget = Data.reduce(function (indexOfTarget, element, currentIndex) {
    return (element.name === 'hypno7oad') ? currentIndex : indexOfTarget;
}, -1);

Answer 21

Maybe the Object.keys, Object.entries, and Object.values methods might help.

Answer 22

Using Underscore.js:

var index = _.indexOf(_.pluck(item , 'name'), 'Nick');