遍历JavaScript中的JSON哈希

Question

Json:

{
 "comments":[
    {"id":1,"author_name":null,"comment_text":null,"url":"http://localhost:3000/comments/1.json"},
    {"id":2,"author_name":null,"comment_text":null,"url":"http://localhost:3000/comments/2.json"},{"id":3,"author_name":"Yerassyl","comment_text":"Hello world!","url":"http://localhost:3000/comments/3.json"},
    {"id":4,"author_name":"Yerassyl","comment_text":"hi there","url":"http://localhost:3000/comments/4.json"}
 ]
}

How to iterate over each comment in comments. I want something like that:

//pseudocode
comments.each(key,value){
// do something
}

I tried map, but map is for arrays.

EDIT: If i delete root node 'comments' i can use .map:

var commentNodes = this.props.comments.map(function(comment,index){
      });

Ignore this.props, it is actually React.js.
console.log(this.props.comments) returns my json objects with root node 'comments'

Answer 1

Assuming you have

var obj = {
 "comments":[
    {"id":1,"author_name":null,"comment_text":null,"url":"http://localhost:3000/comments/1.json"},
    {"id":2,"author_name":null,"comment_text":null,"url":"http://localhost:3000/comments/2.json"},{"id":3,"author_name":"Yerassyl","comment_text":"Hello world!","url":"http://localhost:3000/comments/3.json"},
    {"id":4,"author_name":"Yerassyl","comment_text":"hi there","url":"http://localhost:3000/comments/4.json"}
 ]
};

You can just do, for example,

obj.comments.map(function (comment) {
    console.log(comment);
});

Answer 2

Assuming you have already JSON.parse d the string, you can use forEach to iterate. Map is only for returning a new array from your existing values.

this.props.comments.comments.forEach(function(value, index) {
    console.log(value, index);
});

edit: Sounds like this.props.comments is the root object. Hence the accessor above

Answer 3

Firstly you have to parse your JSON data:

var json = '{
 "comments":[
    {"id":1,"author_name":null,"comment_text":null,"url":"http://localhost:3000/comments/1.json"},
{"id":2,"author_name":null,"comment_text":null,"url":"http://localhost:3000/comments/2.json"},{"id":3,"author_name":"Yerassyl","comment_text":"Hello world!","url":"http://localhost:3000/comments/3.json"},
{"id":4,"author_name":"Yerassyl","comment_text":"hi there","url":"http://localhost:3000/comments/4.json"}
 ]
}';
var data = JSON.parse(json);

And then you can proceed and loop throught comments like this:

data.comments.forEach(function(comment, index) {
    console.log("Comments["+index+"]: "+comment);
});

Note:

Once your JSON is parsed you will get an object including an array of comments so you can easily use all the Array.prototype methods with it including forEach and map .