Javascript 数组，由一组变量构建

Question

以下变量是通过Car原型定义的：

var Car = function(maker, type, model) {
  this.maker = maker;
  this.type = type;
  this.model = model;
}

var golf = new Car('VW', 'Hatchback', 'Golf');
var sentra = new Car('Nissan', 'Sedan', 'Sentra');
var _328i = new Car('BMW', 'Convertible', "328i");
var gallardo = new Car('Lamborghini', 'Convertible', "Gallardo");
var corniche = new Car('Rolls Royce', 'Sedan', "Corniche");

Car.prototype.year = 0;

golf.year = 2015;
sentra.year = 2010;
_328i.year = 2019;
gallardo.year = 2020;
corniche.year = 1998;  

如何为属性 maker 构建一个 var 值数组

可能会像这样控制台日志：

(5) ['VW'、'Nissan'、'BMW'、'Lamborghini'、'Roll Royce']

Answer 1

您可以创建汽车实例数组并使用map 函数

console.log(
  [golf, sentra, _328i, gallardo, corniche].map((car) => car.maker)
)

Answer 2

对此有很多解决方案。首先，您需要为所有汽车创建一个数组，然后使用一种方法对每辆汽车进行迭代以获取汽车制造商。

这里有两个例子：

var Car = function (maker, type, model) {
  this.maker = maker;
  this.type = type;
  this.model = model;
}

Car.prototype.year = 0;

var golf = new Car ('VW', 'Hatchback', 'Golf');
var sentra = new Car ('Nissan', 'Sedan', 'Sentra');
var _328i = new Car ('BMW', 'Convertible', "328i");
var gallardo = new Car ('Lamborghini', 'Convertible', "Gallardo", 2020);
var corniche = new Car('Rolls Royce', 'Sedan', "Corniche");

golf.year = 2015;
sentra.year = 2010;
_328i.year = 2019;
gallardo.year = 2020;
corniche.year = 1998;

var cars = [golf, sentra, _328i, gallardo, corniche]
var carsMakers = []

for(var i = 0; i < cars.length; i++) {
  var c = cars[i]
  carsMakers.push(c.maker)
}
console.log(carsMakers)

var carsMakers2 = cars.map(function(c) { return c.maker });
console.log(carsMakers2)

Answer 3

就像map 方法，但使用Array.prototype.from：

var Car = function (maker, type, model) {
this.maker = maker;
this.type = type;
this.model = model;
}
var golf = new Car ('VW', 'Hatchback', 'Golf');
var sentra = new Car ('Nissan', 'Sedan', 'Sentra');
var _328i = new Car ('BMW', 'Convertible', "328i");
var gallardo = new Car ('Lamborghini', 'Convertible', "Gallardo");
var corniche = new Car('Rolls Royce', 'Sedan', "Corniche");

Car.prototype.year = 0;

golf.year = 2015;
sentra.year = 2010;
_328i.year = 2019;
gallardo.year = 2020;
corniche.year = 1998;

// Solution here
const makersList = Array.from([golf, sentra, _328i, gallardo, corniche], car => car.maker );

// should print an array of makers string names
console.log(makersList);