Loop through array of objects to find object with matching property

Question

I have 1 array, one with a list of all my users with unique IDs. I have an object which contains contains a selected groups information. Part of that information is the owners ID. I'm trying to figure out, how do I get the users's information given the groups owner ID? For example, the student group object has an owner ID of 70, there's a user on my sites who's ID is 70...how do I match them up?

users: 
[  { 
id: 68
name: mike
domain: i:0#.f|admembers|mike.ca
email: mike.ca
isAdmin: False
 }, etc etc ]

selectedGroup:  { 
name: Students
id: 78
description: 
owner: 70
ownerIsUser: True
 } 

Answer 1

You'll have to loop through users:

var i = users.length,
    ownerData;

while(i--) {
    if(selectedGroup.owner == users[i].id) {
        ownerData = users[i];
        break;
    }
}

Or you could use Array.filter():

var ownerData = users.filter(function(user) {
    return user.id === selectedGroup.owner;
})[0];

Answer 2

In ECMAScript 6, you could use the native Array.find method:

var selectedUser = users.find( function( user ){
  return user.id === 70;
} );

Seeing as only the latest Firefox supports this for the moment, you could use a library like underscore.js:

var selectedUser = _.find( users, function( user ){
  return user.id === 70;
} );

…or you could use a wrapper around the slightly less recent forEach method:

var selectedUser;

users.forEach( function( user ){
  if( user.id === 70 ){
    selectedUser = user;
  }
} );

But if you want to use script that'll support legacy browsers without using libraries, you'll need a for loop:

var selectedUser;

for( var i = 0; i < users.length; i++ ){
  if( users[ i ].id === 70 ){
    selectedUser = users[ i ];

    break;
  }
};