speed.js

var userIds = [];

// Create dummy ids
for (var i=0; i < 10000; i++) {
	userIds.push('id-'+new Date().getTime()+Math.random()*100000000000000000+''+(Math.random()*100000000000000000)+''+(Math.random()*100000000000000000));
};

// Populate array with ids and users attached
var usersArr = []
for (var i=0,l=users.length; i < l; i++) {
	usersArr.push({
		'id': userIds[i]
		, 'name': 'mape-'+userIds[i]
	});
};

// Populate object with ids and users attached
var usersObj = []
for (var i=0,l=users.length; i < l; i++) {
	usersObj[userIds[i]] = {
		'name': 'mape-'+userIds[i]
	}
};

// Generate an id to find
var randomId = userIds[Math.floor(Math.random()*userIds.length)];

console.log('Find: '+randomId);

console.time('Fetch in array')
for (var i=0,l=users.length; i < l; i++) {
	if (usersArr[i].id === randomId)
	{
		console.dir(usersArr[i]);
		break;
	}
};
console.timeEnd('Fetch in array')

console.time('Fetch in object')
console.dir(usersObj[randomId]);
console.timeEnd('Fetch in object')