2.map

 * 
 * 假定有一个数值数组(A),将A数组中的值以双倍的形式放到B数组 
 */

 var numbers = [1,2,3];

 var doubledNumbers = [];

// es5
for(var i = 0; i < numbers.length; i++){
  doubledNumbers.push(numbers[i] * 2);
}

// console.log(doubledNumbers);
// es5 
for(var i = 0; i < doubledNumbers.length; i++){
  // console.log(doubledNumbers[i]);
}

// es6 map
var doubled = numbers.map(function(number){
    return number * 2;
})

// console.log(doubled);

// es6 forEach
doubled.forEach(function(number){
    console.log(number);
})


/** 场景2
 * 
 * 假定有一个对象数组(A),将A数中对象某个属性的值存储到B数组中
 */

var cars = [
  {model:"Buick",price:"CHEAP"},
  {model:"BMW",price:"expensive"}
];

var prices = cars.map(function(car){
    return car.price;
})

console.log(prices);