Copy object to an array

Question

I am trying to copy an object userinfo into an array. I keep getting undefined when I try to console log the new array. Any help will be appreciated!

JS:

var JSONstring = [{
  "name": "test",
  "properties": {
    "age": "19r",
    "userinfo": {
      "city": "Dallas",
      "state": "Texas"
    }
  }
}];

$(document).ready(function() {
  var userinfo = {};
  for (var i = 0; i < JSONstring.length; i++) {
    var user = JSONstring[i].properties.userinfo;
    if (user === undefined) {
      continue;
    } else if (userinfo[user] === undefined) {
      userinfo[user] = [];
      userinfo[user].push(i);
    } else {
      userinfo[user].push(i);
    }
  }
  console.log(userinfo[0]);
});

JSFiddle Demo

userinfo[user] doesn't make a whole lot of sense, user is either undefined or an object. object keys are always strings. — user400654
– user400654, Commented Apr 21, 2017 at 21:09
So there are a few problems with object types in your example. Your JSONstring var is an object, it does not have a .length member. Your userinfo "array" is also an object. — Ken
– Ken, Commented Apr 21, 2017 at 21:11
Please not that the variable name JSONstring is extremely misleading since the value of the variable is an array, not a string (containing JSON). Calling JavaScript objects "JSON" is a (unfortunately) common mistake. — Felix Kling
– Felix Kling, Commented Apr 21, 2017 at 21:11

cнŝdk · Accepted Answer · 2017-04-21 21:34:07Z

2

Actually you have several problems in your current code:

Writing userinfo[user] is incorrect, if you want to access userproperty of userinfoobject you need to give it a string like userinfo["user"] or just directly userinfo.user.
In the end you are trying to log userinfo[0] which is undefined because userinfo is an object and not an array you need to change it to : console.log(userinfo.user[0]).
If you want to store the user object in the array you should replace push(i) with push(user).

Demo:

I tried to refactor your code so it makes sense, here's what you need:

var JSONstring = [{
  "name": "test",
  "properties": {
    "age": "19r",
    "userinfo": {
      "city": "Dallas",
      "state": "Texas"
    }
  }
}];

$(document).ready(function() {
  var userinfo = {};
  for (var i = 0; i < JSONstring.length; i++) {
    var user = JSONstring[i].properties.userinfo;
    if (!user) {
      continue;
    } else if (!userinfo.user) {
      userinfo.user = [];
      userinfo.user.push(user);
    } else {
      userinfo.user.push(user);
    }
  }
  console.log(userinfo.user[0]);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Note:

The condition in the if block if (userinfo[user] === undefined) can simply be written if(!userinfo.user)

edited Apr 21, 2017 at 21:34

answered Apr 21, 2017 at 21:23

cнŝdk

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2 Comments

user4756836 Over a year ago

Why is the console.log coming as 0 now?

cнŝdk Over a year ago

Because it takes i in the loop, we should push(user), I edited my answer.

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