[javascript] How to get index of object by its property in JavaScript?

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?

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 multiply objects inside, if you want know if some object are include on Master object, just put find(MasterObject,'Object to Search'), this function will return the response if exist or not (TRUE or FALSE), I hope help with this, can see the exemple on JSFiddle.

Only way known for me is to looping 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.

Why don't you use a small work-around?

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.

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

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

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.

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

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

theArray.every(function (element, index) {

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

This might be useful

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

Copied this from https://developer.mozilla.org/en/JavaScript/Guide/Working_with_Objects

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

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.

Edit : 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.

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 desired object.

Alternatively to German Attanasio Ruiz's answer, you can eliminate the 2nd 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);

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's function

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);

Using underscore:

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

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

What about this ? :

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

Assuming you are using lodash or underscorejs.

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');

Array.prototype.map is not available on IE7 or IE8. ES5 Compatibility

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

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

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');