Javascript 如何在javascript中迭代（键，值）？

How to iterate (keys, values) in javascript?

提问by nbroeking

I have a dictionary that has the format of

我有一本字典，格式为

dictionary = {0: {object}, 1:{object}, 2:{object}}

How can I iterate through this dictionary by doing something like

我怎样才能通过做类似的事情来遍历这本字典

for((key,value) in dictionary){
  //Do stuff where key would be 0 and value would be the object
}

回答by thefourtheye

tl;dr

tl;博士

1. In ECMAScript 5, it is not possible.
2. In ECMAScript 2015, it is possible with Maps.
3. In ECMAScript 2017, it would be readily available.

1. 在 ECMAScript 5 中，这是不可能的。
2. 在 ECMAScript 2015 中，可以使用Maps。
3. 在 ECMAScript 2017 中，它很容易获得。

ECMAScript 5:

ECMAScript 5：

No, its not possible with objects.

不，它不可能与对象。

You should either iterate with for..in, or Object.keys, like this

您应该像这样使用for..in, 或进行迭代Object.keys

for (var key in dictionary) {
    // check if the property/key is defined in the object itself, not in parent
    if (dictionary.hasOwnProperty(key)) {           
        console.log(key, dictionary[key]);
    }
}

Note:The ifcondition above is necessary, only if you want to iterate the properties which are dictionaryobject's very own. Because for..inwill iterate through all the inherited enumerable properties.

注意：上述if条件是必要的，仅当您要迭代dictionary对象自己的属性时。因为for..in会遍历所有继承的可枚举属性。

Or

或者

Object.keys(dictionary).forEach(function(key) {
    console.log(key, dictionary[key]);
});

---

---

ECMAScript 2015

ECMAScript 2015

In ECMAScript 2015, you can use Mapobjects and iterate them with Map.prototype.entries. Quoting example from that page,

在 ECMAScript 2015 中，您可以使用Map对象并使用Map.prototype.entries. 引用该页面的示例，

var myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

var mapIter = myMap.entries();

console.log(mapIter.next().value); // ["0", "foo"]
console.log(mapIter.next().value); // [1, "bar"]
console.log(mapIter.next().value); // [Object, "baz"]

Or iterate with for..of, like this

或者for..of像这样迭代

'use strict';

var myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

for (const entry of myMap.entries()) {
  console.log(entry);
}

Output

输出

[ '0', 'foo' ]
[ 1, 'bar' ]
[ {}, 'baz' ]

Or

或者

for (const [key, value] of myMap.entries()) {
  console.log(key, value);
}

Output

输出

0 foo
1 bar
{} baz

---

---

ECMAScript 2017

ECMAScript 2017

ECMAScript 2017 would introduce a new function Object.entries. You can use this to iterate the object as you wanted.

ECMAScript 2017 将引入一个新函数Object.entries。您可以根据需要使用它来迭代对象。

'use strict';

const object = {'a': 1, 'b': 2, 'c' : 3};
for (const [key, value] of Object.entries(object)) {
  console.log(key, value);
}

Output

输出

a 1
b 2
c 3

回答by alex10

Try this:

尝试这个：

dict = {0:{1:'a'}, 1:{2:'b'}, 2:{3:'c'}}
for (var key in dict){
  console.log( key, dict[key] );
}

0 Object { 1="a"}
1 Object { 2="b"}
2 Object { 3="c"}

回答by Loilo

The Object.entries()method has been specified in ES2017 (and is supported in all modern browsers):

该Object.entries()方法已在 ES2017 中指定（并且在所有现代浏览器中均受支持）：

for (const [ key, value ] of Object.entries(dictionary)) {
    // do something with `key` and `value`
}

Explanation:

解释：

• Object.entries()takes an object like { a: 1, b: 2, c: 3 }and turns it into an array of key-value pairs: [ [ 'a', 1 ], [ 'b', 2 ], [ 'c', 3 ] ].

• With for ... ofwe can loop over the entries of the so created array.

• Since we are guaranteedthat each of the so iterated array items is itself a two-entry array, we can use destructuringto directly assign variables keyand valueto its first and second item.

• Object.entries()采用类的对象{ a: 1, b: 2, c: 3 }，并把它变成键-值对的数组：[ [ 'a', 1 ], [ 'b', 2 ], [ 'c', 3 ] ]。

• 随着for ... of我们可以遍历所谓创建的数组的条目。

• 由于我们保证，每个迭代使阵列项目本身是一个双项阵列，我们可以用解构直接分配变量key，并value在其第一和第二项。

回答by Dhaval Chaudhary

You can do something like this :

你可以这样做：

dictionary = {'ab': {object}, 'cd':{object}, 'ef':{object}}
var keys = Object.keys(dictionary);

for(var i = 0; i < keys.length;i++){
   //keys[i] for key
   //dictionary[keys[i]] for the value
}

回答by AMACB

Try this:

尝试这个：

var value;
for (var key in dictionary) {
    value = dictionary[key];
    // your code here...
}

回答by Steve

WELCOME TO 2020 *Drools in ES6*

欢迎来到 2020 * ES6 中的 Drools*

Theres some pretty old answers in here - take advantage of destructuring. In my opinion this is without a doubt the nicest (very readable) way to iterate an object.

这里有一些非常古老的答案 - 利用解构。在我看来，这无疑是迭代对象的最好（非常易读）的方式。

Object.entries(myObject).forEach(([k,v]) => {
    console.log("The key: ",k)
    console.log("The value: ",v)
})

回答by Jonathan

I think the fast and easy way is

我认为快速简便的方法是

Object.entries(event).forEach(k => {
    console.log("properties ... ", k[0], k[1]); });

just check the documentation https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries

只需查看文档 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries

回答by deeshank

using swagger-ui.js

使用 swagger-ui.js

you can do this -

你可以这样做 -

_.forEach({ 'a': 1, 'b': 2 }, function(n, key) {
    console.log(n, key);
 });

回答by kloddant

As an improvement to the accepted answer, in order to reduce nesting, you could do this instead:

作为对已接受答案的改进，为了减少嵌套，您可以这样做：

for (var key in dictionary) {
    if (!dictionary.hasOwnProperty(key)) {           
        continue;
    }
    console.log(key, dictionary[key]);
}

回答by Michael Piper

You can use below script.

您可以使用以下脚本。

var obj={1:"a",2:"b",c:"3"};
for (var x=Object.keys(obj),i=0;i<x.length,key=x[i],value=obj[key];i++){
    console.log(key,value);
}

outputs
1 a
2 b
c 3

输出
1 a
2 b
c 3