类型脚本中的数组 [英] Arrays in type script

问题描述

下面是适用于我的代码

  --------------------------------------- --------------- 
 class Book {
 public BookId：number; 
 public标题：string; 
 public作者：string; 
 public价格：number; 
 public描述：string; 
} 
 class dataservice {
 getproducts（）{
 var bk = new Book（）; 
 bk.Author =vamsee; 
 bk.BookId = 1; 
 var bks：Book [] = [bk，bk]; 
 
 return bks.length; 
} 
} 
 
 var ds = new dataservice（）; 
 var button = document.createElement（'button'）; 
 
 button.onclick = function（）{
 
 alert（ds.getproducts（）。toString（））; 
} 
 
 document.body.appendChild（button）; 
 ---------------------------------------------- ---------------- 
  

当我更改我的代码如下面，当试图为数组项赋值时失败。

  var bks：Book [] = new Book [2] 
 bks [0] .Author =vamsee; 
 bks [0] .BookId = 1; 
 return bks.length; 
  

对于我在循环中添加对象，我必须以第二种方式。

解决方案

这是一个非常c＃类型的代码：

  var bks：Book [] = new Book [2]; 
  

在Javascript / Typescript中，你不会像这样分配内存，这意味着完全不同。这是你将如何做你想做的：

  var bks：Book [] = []; 
 bks.push（new Book（））; 
 bks [0] .Author =vamsee; 
 bks [0] .BookId = 1; 
 return bks.length; 
  

现在来解释 new Book [2]; 意思。这实际上意味着对Book [2]的值调用new运算符。例如：

  Book [2] = function（）{alert（hey）;} 
 var foo =新书[2] 
  

尝试

I am finding difficulty declaring array in typescript and accessing it.

below is the code working for me

------------------------------------------------------
 class Book {
    public BookId: number;
    public Title: string;
    public Author: string;
    public Price: number;
    public Description: string;
}
class dataservice {
      getproducts() {
         var bk = new Book();
        bk.Author = "vamsee";
        bk.BookId = 1;
        var bks: Book[] = [bk,bk];

      return bks.length;
    }
}

var ds = new dataservice();
var button = document.createElement('button');

button.onclick = function () {

    alert(ds.getproducts().toString());
}

document.body.appendChild(button);
--------------------------------------------------------------

When I change my code as below it fails when trying to assign value to array item.

 var bks: Book[] = new Book[2];
bks[0].Author = "vamsee";
        bks[0].BookId = 1;
      return bks.length;

For me to add object in a loop I have to do it the second way.

解决方案

This is a very c# type of code:

var bks: Book[] = new Book[2];

In Javascript / Typescript you don't allocate memory up front like that, and that means something completely different. This is how you would do what you want to do:

var bks: Book[] = [];
bks.push(new Book());
bks[0].Author = "vamsee";
bks[0].BookId = 1;
return bks.length;

Now to explain what new Book[2]; would mean. This would actually mean that call the new operator on the value of Book[2]. e.g.:

Book[2] = function (){alert("hey");}
var foo = new Book[2]

and you should see hey. Try it

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