Javascript - Running through JSON object using for loop

Question

I'm new to JS and I'm trying to loop through the following JSON:

myLogger - myLogger - JSON ARRAY - {"dummmysetsJSONArr":[{"entryID":"1","distance":"100","calories":"50"},{"entryID":"2","distance":"200","calories":"100"},{"entryID":"3","distance":"300","calories":"150"},{"entryID":"4","distance":"400","calories":"200"},{"entryID":"5","distance":"500","calories":"250"},{"entryID":"6","distance":"600","calories":"300"}],"success":1}

but my console line keep printing:

myLogger - undefined - undefined - undefined

I've seen successful solutions such as these which seem not be working for me.

My for loop attempts are as below:

    for (var key in jsonarry) {
      if (jsonarry.hasOwnProperty(key)) {
        myLogger(jsonarry[key].entryID + " - " + jsonarry[key].distance + " - " + jsonarry[key].calories);
      }
    }

    /*
    for (var key in jsonarry) {
      if (jsonarry.hasOwnProperty(key)) {
        myLogger(jsonarry[0].entryID + " - " + jsonarry[1].distance + " - " + jsonarry[2].calories);
      }
    }
    */

Here's my full JS:

    google.load("visualization", "1", {packages:["corechart"]});

google.setOnLoadCallback(drawVisualization);

function drawVisualization() {

  var req = false;
  var jsonarry;

  try {
      // most browsers
      req = new XMLHttpRequest();

      myLogger("myLogger - XMLHttpRequest() created");
  } catch (e){
      // IE
      try{
          req = new ActiveXObject("Msxml2.XMLHTTP");

          myLogger("myLogger - req = new ActiveXObject(Msxml2.XMLHTTP);");          
      } catch (e) {
          // try an older version
          try{
              req = new ActiveXObject("Microsoft.XMLHTTP");

              myLogger("myLogger - req = new ActiveXObject(Microsoft.XMLHTTP);");               
          } catch (e){

          }
      }
  }

  if (!req) { 
    myLogger("req === false");
  } else {

    myLogger("req === true");
  }

  // Use onreadystatechange property
  req.onreadystatechange = function() {

       //myLogger("myLogger - req.onreadystatechange = function(){");

      if(req.readyState == 4) {

          myLogger("myLogger - req.readyState == 4");

          if(req.status === 200) {

            myLogger("myLogger - req.status === 200");

            jsonarry = req.responseText;

            myLogger("myLogger - JSON ARRAY - " + jsonarry);

            myLogger(" ------------- ");

            var obj = JSON.parse(jsonarry);

            myLogger("jsonarry.length == " + jsonarry.length);

            for (var key in jsonarry) {
              if (jsonarry.hasOwnProperty(key)) {
                myLogger(jsonarry[key].entryID + " - " + jsonarry[key].distance + " - " + jsonarry[key].calories);
              }
            }

            /*
            for (var key in jsonarry) {
              if (jsonarry.hasOwnProperty(key)) {
                myLogger(jsonarry[0].entryID + " - " + jsonarry[1].distance + " - " + jsonarry[2].calories);
              }
            }
            */
          } else {
            myLogger("myLogger - req.status == " + req.status);
          }

          //return req.status === 200 ? success(req.responseText) : error(req.status)
      } else {
          myLogger("myLogger - req.readyState != 4 i.e. req.readyState === " + req.readyState);
      }
  }

  req.open("GET", 'http://www.dummyurl/dbread.php', true);

  req.send(null); 
}

function myLogger(content) {
    if (window.console && window.console.log) {
        console.log("myLogger - " + content);
    }
}

possible duplicate of [Parse JSON in JavaScript?](http://stackoverflow.com/questions/4935632/parse-json-in-javascript) — Abhishek, Apr 15 '15 at 06:09

score 0 · Accepted Answer · answered Apr 15 '15 at 06:05

0

You are parsing the JSON string and instead of looping through the parsed value, you are looping through JSON strring.

var obj = JSON.parse(jsonarry);

myLogger("jsonarry.length == " + jsonarry.length);

for (var key in jsonarry) {
    if (jsonarry.hasOwnProperty(key)) {
        myLogger(jsonarry[key].entryID + " - " + jsonarry[key].distance + " - " + jsonarry[key].calories);
    }
}

Use like below.

var obj = JSON.parse(jsonarry);

myLogger("jsonarry.length == " + jsonarry.length);

for (var key in obj) {
    if (jsonarry.hasOwnProperty(key)) {
        myLogger(jsonarry[key].entryID + " - " + jsonarry[key].distance + " - " + jsonarry[key].calories);
    }
}

But, why are you looping through object ? You need to loop through array inside that object right ?

answered Apr 15 '15 at 06:05

Vigneswaran Marimuthu

2,452
13
16

Thanks .. I get my error .. I was iterating through the raw JSON as opposed to the object ... – ANM Apr 15 '15 at 17:08
After implementing your suggestion .. it seems my JSON data is failing the if check in the for loop .. any ideas why? – ANM Apr 15 '15 at 17:23
@ANM By "if check" what you mean ? You meant `jsonarray.hasOwnProperty(key)` ? – Vigneswaran Marimuthu Apr 16 '15 at 05:34

Bob · Answer 2 · 2015-04-15T06:19:53.980

You need to work with the parsed JSON result that you assigned to obj instead of the raw JSON text in jsonarry

Also "dummmysetsJSONArr" is an array of objects.

Try this:

for (var key in obj) {
      if (obj.hasOwnProperty(key)) {
           var list=obj[key];
           list.forEach(function(item){
               myLogger(item.entryID + " - " + item.distance + " - " + item.calories);
           });
      }
 }

Also avoid removing letters from variable names such as jsonarry it will eventually lead to confusion.

Javascript - Running through JSON object using for loop

2 Answers2

Linked