Javascript对象如何通过for语句进行迭代？ [英] How can a Javascript object become iterable with for...of statement?

问题描述

我想设置选项[Symbol.iterator] 属性，以便迭代我用创建的简单对象。 .of 声明：

I would like to set the options[Symbol.iterator] property in order to iterate on the simple objects I create with the for...of statement :

options = {
  male: 'John',
  female: 'Gina',
  rel: 'Love'
};


for(let p of options){
  console.log(`Property ${p}`);
};

但此代码给出了以下错误：

But this code gives me the following error:

 array.html:72 Uncaught TypeError: options[Symbol.iterator] is not a function

如何在上面的简单对象上设置正确的迭代器函数？

How I can set the right iterator function on a simple object as above?

Solved

Solved

 // define the Iterator for the options object 
 options[Symbol.iterator] = function(){

     // get the properties of the object 
     let properties = Object.keys(this);
     let count = 0;
     // set to true when the loop is done 
     isDone = false;

     // define the next method, need for iterator 
     let next = () => {
        // control on last property reach 
        if(count >= properties.length){
           isDone = true;
        }
        return {done:isDone, value: this[properties[count++]]};
     }

     // return the next method used to iterate 
     return {next};
  };

我可以将用于...... 我的对象上的语句现在是可迭代的：

And I can use the for...of statement on my object now iterable :

 for(let property of options){
   console.log(`Properties -> ${property}`);
 }

推荐答案

使用 for ... of 循环你应该使用 [Symbol.iterator] key为你的对象定义一个合适的迭代器。

To use for...of loop you should define an appropriate iterator for your object using [Symbol.iterator] key.

这是一个可能的实现：

let options = {
  male: 'John',
  female: 'Gina',
  rel: 'Love',
  [Symbol.iterator]: function * () {
    for (let key in this) {
      yield [key, this[key]] // yield [key, value] pair
    }
  }
}

尽管在大多数情况下，最好使用普通的迭代对象...在循环中。

Though, in most cases it'll be better to iterate over objects using plain for...in loop instead.

或者你可以使用 Object.keys ， Object.values 或 Object.entries （ES7）。

Alternatively you could convert your object to iterable array using Object.keys, Object.values or Object.entries (ES7).

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