function a(input) {
  var index = [];
  var item;
  for (var i=0; i<input.length; i++) {
    item = input[i];
    if (index.indexOf(item) === -1) {
      index.push(item);
    }
  }
  return index;
}
function b(input) {
  var index = {};
  var item;
  for (var i=0; i<input.length; i++) {
    item = input[i];
    if (index[item] === undefined) {
      index[item] = true;
    }
  }
  return index;
}
function c(input) {
  var index = {};
  var item;
  for (var i=0; i<input.length; i++) {
    item = input[i];
    index[item] = true;
  }
  return index;
}

function test(f, input, times) {
  for (var i=0; i<times; i++) {
    f(input());
  }
}

function first(amount) {
  return function() {
    var data = [];
    for (var i=0; i<amount; i++) {
      data.push(i);
    }
    return data;
  }
}

function random(amount, range) {
  return function() {
    var data = [];
    for (var i=0; i<amount; i++) {
      data.push(Math.floor(Math.random()*range));
    }
    return data;
  }
}

var testAmount = 1000;
var testRange = 100;
var testTimes = 10000;

console.log('amount, range, times');
console.log(testAmount+', '+testRange+', '+testTimes);
console.log('--------------------')

console.time('a'); test(a, random(testAmount, testRange), testTimes); console.timeEnd('a');
console.time('b'); test(b, random(testAmount, testRange), testTimes); console.timeEnd('b');
console.time('c'); test(c, random(testAmount, testRange), testTimes); console.timeEnd('c');