javascript - 使用变量访问构造函数并获取想要的字符串

Question

function Title(mainTitle){
  this.mainTitle = mainTitle;
}

var projectTitle1 = new Title("Project-1 Main Title"),
projectTitle2 = new Title("Project-2 Main Title"),
projectTitle3 = new Title("Project-3 Main Title"),
projectTitle4 = new Title("Project-4 Main Title");

我喜欢访问构造函数并提取与给定索引(1-4)相关的标题。我尝试了以下方法:

  var index = 4,
  x = "projectTitle" + index,
  y = projectTitle.mainTitle;

console.log(y) 返回未定义。

Answer 1

运行后您无法“访问构造函数”。然而，您可以做的是将每个实例化放入一个数组中，并访问适当的索引:

function Title(mainTitle){
  this.mainTitle = mainTitle;
}
const titles = [
  new Title("Project-1 Main Title"),
  new Title("Project-2 Main Title"),
  new Title("Project-3 Main Title"),
  new Title("Project-4 Main Title"),
];
const getTitle = titleNum => titles[titleNum - 1].mainTitle;
console.log(getTitle(4));
console.log(getTitle(2));

当然，您必须按顺序将项目添加到 titles 中。如果这不能可靠，另一种可能性是将每个title放入一个对象中，该对象由其mainTitle中的数字索引。