Loop through JSON with javascript

Question

Here are many examples how to iterate over javascript Objects. This works actually fine for me

    var text = '{"employees":[' +
'{"firstName":"John","lastName":"Doe" },' +
'{"firstName":"Anna","lastName":"Smith" },' +
'{"firstName":"Peter","lastName":"Jones" }]}';

obj = JSON.parse(text);
document.getElementById("demo").innerHTML =
obj.employees[1].firstName + " " + obj.employees[1].lastName;

But didn't work out how to iterate over the values in obj. Tried like this

    for(var k in obj) {
    if (obj.hasOwnProperty(k)) {
        if (obj.hasOwnProperty(k)) {
             out +=("Key is " + k + ", value is" + obj[k].firstName);
        }
    }
}

but failed. As you can see stolen from examples. If someone can help with some javascript code to iterate over the JSON key-value pairs ?

Why are you writing text out a string then parsing it instead of just declaring as an object in the first place, which would be much easier programatically and semantically? — Popnoodles
– Popnoodles, Commented Aug 18, 2015 at 13:56
@Popnoodles: I would assume to emulate receiving it from an ajax call or similar (but it's an assumption). — T.J. Crowder
– T.J. Crowder, Commented Aug 18, 2015 at 13:59
Cerbrus this was just a trie to iterare over both key and values. Popnoodles...because I don't know js good enough....anyhow do you have an example how to iterate such a json array ? — user3732793
– user3732793, Commented Aug 18, 2015 at 14:06

Community · Accepted Answer · 2017-05-23 12:06:12Z

2

Once parsed, your obj variable refers to an object with an employees property which refers to an array. So:

obj.employees.forEach(function(employee) {
    // ...
});

or

var i, employee;
for (i = 0; i < obj.employees.length; ++i) {
    employee = obj.employees[i];
    // ...
}

...or any of the several other ways outlined in this answer.

edited May 23, 2017 at 12:06

CommunityBot

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answered Aug 18, 2015 at 14:01

T.J. Crowder

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1 Comment

user3732793 Over a year ago

excellent thanks, I like the first one it's small and straight forward

Laxmikant Dange · Accepted Answer · 2015-08-18 14:01:15Z

1

Your example json has parent key employees, which has child array of objects. Then you have to loop through array if you know the key else you can use Object.keys which will return list of keys in object in array format.

var text = '{"employees":[' +
  '{"firstName":"John","lastName":"Doe" },' +
  '{"firstName":"Anna","lastName":"Smith" },' +
  '{"firstName":"Peter","lastName":"Jones" }]}';

obj = JSON.parse(text);

Object.keys(obj).forEach(function(k) { //Loop through keys of obj.
  obj[k].forEach(function(elm) {  //Loop through all elements of first object array
    console.log(elm.firstName+"_"+elm.lastName)
  })
})

answered Aug 18, 2015 at 14:01

Laxmikant Dange

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Comments

Xlander · Accepted Answer · 2015-08-18 14:03:33Z

0

It's not working as you are trying to access obj["employees"].firstName which does not exist.

for(var k in obj) {
  if (obj.hasOwnProperty(k)){
    var employee = obj[k];
    for(var i in employee){
      out +="Key is " + i + ", value is" + employee[i].firstName;
    }
  }
}

OR

var employee = obj["employees"];
for(var i in employee){
  out +="Key is " + i + ", value is" + employee[i].firstName;
}

answered Aug 18, 2015 at 14:03

Xlander

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