Iterate over array of objects

Question

I have a JSON string like this

 var json =  '{ "Comments": 
    [
      { "Id" : 1,"Comment" : "Test comment","Name" : "Yogesh","Child" : 0},
      { "Id" : 2,"Comment" : "Test comment II","Name" : "Yogesh","Child" : 0}
    ] 
    }';

and I'm trying to iterate over the objects as such:

var parsedJSON = $.parseJSON(json);

var html = "";    
for (comment in parsedJSON.Comments) {
  html += "Id: " + comment.Id;
  html += "Comment: " + comment.Comment;
  html += "Name: " + comment.Name;
  html += "Child: " + comment.Child;
  html += "<br/>";
}

But here comment in for loop becomes 0 and 1 only, I mean not an object but just a string, how can I iterate over this array?

You are not iterating over JSON, you are iterating over a JavaScript array. I corrected your question accordingly. You should use a for loop for that. You might also read about arrays in JavaScript. — Felix Kling
– Felix Kling, Commented Jul 28, 2012 at 14:03

thecodeparadox · Accepted Answer · 2013-04-18 21:58:17Z

6

var json = '{ "Comments": [{ "Id" : 1,"Comment" : "Test comment","Name" : "Yogesh","Child" : 0},{ "Id" : 2,"Comment" : "Test comment II","Name" : "Yogesh","Child" : 0}] }';

var parsedJSON = $.parseJSON(json), // jsonData should json
    html = "",
    comments =parsedJSON.Comments; // keeping reference of parsedJSON and its an Array

// Here key will give 0, 1 etc ie. index of array

for (var key in comments) {
    html += "Id: " + comments[key].Id;
    html += "Comment: " + comments[key].Comment;
    html += "Name: " + comments[key].Name;
    html += "Child: " + comments[key].Child;
    html += "<br/>";
}

Demo

edited Apr 18, 2013 at 21:58

answered Jul 28, 2012 at 14:03

thecodeparadox

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4 Comments

Niet the Dark Absol Over a year ago

Giving code that doesn't work (ReferenceError: comments is not defined) with no explanation? Boo.

iCollect.it Ltd Over a year ago

@Kolink: Perhaps a basic knowledge of correcting JS typos is assumed in the javascript tag :) I have changed the ";" to a "," to rectify the declaration error.

iCollect.it Ltd Over a year ago

+1 for showing an interesting alternative to basic for-next indexing.

user2153497 Over a year ago

also, see this for a forEach varsion of this solution: jsfiddle.net/Jrg2k/5

Niet the Dark Absol · Accepted Answer · 2012-07-28 14:03:13Z

2

You seem to have misunderstood how for..in loops work. comment will iteratively be the keys of the array. In any case, you should not use for..in on an array, only objects - and even then with caution.

var l = parsedJSON.Comments.length, i, comment;
for( i=0; i<l; i++) {
    comment = parseJSON.Comments[i];
    // do stuff with comment
}

answered Jul 28, 2012 at 14:03

Niet the Dark Absol

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1 Comment

yogi Over a year ago

I had tried it very first, but parsedJSON.Comments doesn't had any definition for length.

M Abbas · Accepted Answer · 2012-07-28 14:06:26Z

0

YOu can try this:

     var JsonData =  { "Comments":
        [
          { "Id" : 1,"Comment" : "Test comment","Name" : "Yogesh","Child" : 0},
          { "Id" : 2,"Comment" : "Test comment II","Name" : "Yogesh","Child" : 0}
        ]
        };

    var html = "";    
    for (var i = 0; i < JsonData.Comments.length; i++) {
      comment = JsonData.Comments[i];
      html += "Id: " + comment.Id;
      html += " Comment: " + comment.Comment;
      html += " Name: " + comment.Name;
      html += " Child: " + comment.Child;
      html += "<br/>";
    }

alert(html);

answered Jul 28, 2012 at 14:06

M Abbas

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2 Comments

M Abbas Over a year ago

what didn't work exactly? because i tested it and it worked for me, here is my test: jsfiddle.net/VYTpG

yogi Over a year ago

Actually you didn't get the question right, I wasn't talking about a JSON object that you have, I was talking about a JSON string see this jsfiddle.net/VYTpG/1 but anyways thanx for help

Engineer · Accepted Answer · 2012-07-28 14:07:59Z

0

You can use $.each:

var html = ""; 
$.each(parsedJSON.Comments, function(i, comment) {
   html += "Id: " + comment.Id;
   html += "Comment: " + comment.Comment;
   html += "Name: " + comment.Name;
   html += "Child: " + comment.Child;
   html += "<br/>";
}

Alternatively, you could use $.map:

var html = $.map(parsedJSON.Comments, function(comment, i) {
   return "Id: " + comment.Id +
          "Comment: " + comment.Comment +
          "Name: " + comment.Name +
          "Child: " + comment.Child + 
          "<br/>";
}).join('');

answered Jul 28, 2012 at 14:07

Engineer

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Comments

Gerard Sexton · Accepted Answer · 2012-07-28 14:08:38Z

0

Comments holds an array with two elements.

{ "Comments" : [ { 1 }, { 2 }]  ...

So you can access it with

for (var i = 0, len = parsedJSON.Comments.length; i < len; i++) {
    html += "Id: " + parsedJSON.Comments[i].Id;
    html += "Comment: " + parsedJSON.Comments[i].Comment;
    html += "Name: " + parsedJSON.Comments[i].Name;
    html += "Child: " + parsedJSON.Comments[i].Child;
    html += "<br/>";
}

answered Jul 28, 2012 at 14:08

Gerard Sexton

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