Javascript how to parse JSON array

This is my answer:

<!DOCTYPE html>
<html>
   <body>
      <h2>Create Object from JSON String</h2>
      <p>
         First Name: <span id="fname"></span><br> 
         Last Name: <span id="lname"></span><br> 
      </p>
      <script>
         var txt =
           '{"employees":[' +
           '{"firstName":"John","lastName":"Doe" },' +
           '{"firstName":"Anna","lastName":"Smith" },' +
           '{"firstName":"Peter","lastName":"Jones" }]}';
         
         //var jsonData = eval ("(" + txt + ")");
         var jsonData = JSON.parse(txt);
         for (var i = 0; i < jsonData.employees.length; i++) {
             var counter = jsonData.employees[i];
             //console.log(counter.counter_name);
             alert(counter.firstName);
         }
      </script>
   </body>
</html>

Javascript has a built in JSON parse for strings, which I think is what you have:

var myObject = JSON.parse("my json string");

to use this with your example would be:

var jsonData = JSON.parse(myMessage);
for (var i = 0; i < jsonData.counters.length; i++) {
    var counter = jsonData.counters[i];
    console.log(counter.counter_name);
}

Here is a working example

EDIT: There is a mistake in your use of for loop (I missed this on my first read, credit to @Evert for the spot). using a for-in loop will set the var to be the property name of the current loop, not the actual data. See my updated loop above for correct usage

IMPORTANT: the JSON.parse method wont work in old old browsers - so if you plan to make your website available through some sort of time bending internet connection, this could be a problem! If you really are interested though, here is a support chart (which ticks all my boxes).


In a for-in-loop the running variable holds the property name, not the property value.

for (var counter in jsonData.counters) {
    console.log(jsonData.counters[counter].counter_name);
}

But as counters is an Array, you have to use a normal for-loop:

for (var i=0; i<jsonData.counters.length; i++) {
    var counter = jsonData.counters[i];
    console.log(counter.counter_name);
}

Tags:

Javascript

Json

Extjs

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