Get properties in Javascript Object

Question

I have the following javascript object that represents columns of a table that I want user can select to show and analyze based on his/her selection.

var nominalVars   = {
    state     : 'State',    
    messoreg  : 'Messoreg',
    reggeoint : 'RegGeoInt',
    reggeoimd : 'RegGeoImed',
    microreg  : 'Microreg',
    regmetro  : 'RegMetro',
    city      : 'City',
    tipdepe   : 'TipDep',
    nvldepe   : 'NvlDepe',
    prefix    : 'Prefix',
    subord    : 'Subord'
    };

What I need is to retrieve all the properties bellow the last checkbox checked, e.g., If the user selects [state] checkbox, then I want to get [messoreg], [reggeoint], [reggeoimd], [microreg], etc. and them passing the values to an Array.

I don't know if there is it another way to do that but I'm trying to avoid using Swith of If statements.

Don't use an object if ordering is important. Use an array. – Barmar Jun 30 '20 at 20:03 — Barmar, Jun 30 '20 at 20:03

rishabh0211 · Accepted Answer · 2020-07-01T07:48:54.650

2

You should never use an object if you want to keep track of the order. You can use a Map or an Array. The Map object holds key-value pairs and remembers the original insertion order of the keys.

let map = new Map();
map.set('state','State');
map.set('messoreg','Messoreg');
map.set('reggeoint','RegGeoInt');
map.set('reggeoimd','RegGeoImed');
map.set('microreg','Microreg');
map.set('regmetro','RegMetro');
map.set('city','City');
map.set('tipdepe','TipDep');
map.set('nvldepe','NvlDepe');
map.set('prefix','Prefix');
map.set('subord','Subord');

function getKeys(map, afterKey) {
  let shouldAdd = false, res = [];
  for (const key of map.keys()) {
    if (shouldAdd) res.push(key);
    if (key === afterKey) shouldAdd = true;
  }
  return res;
}

function getKeysBefore(map, beforeKey) {
  let shouldAdd = true, res = [];
  for (const key of map.keys()) {
    if (key === beforeKey) shouldAdd = false;
    if (shouldAdd) res.push(key);
  }
  return res;
}

//get keys after 'reggeoint'
let keys;
keys = getKeys(map, 'reggeoint');
document.write(JSON.stringify(keys))

//get keys after 'city'
keys = getKeys(map, 'city');
document.write(JSON.stringify(keys))

//get keys before 'city'
keys = getKeysBefore(map, 'city');
document.write(JSON.stringify(keys))

edited Jul 01 '20 at 07:48

answered Jun 30 '20 at 20:37

rishabh0211

433
4
10

Thank you! One more thing here. How can I do to get all options before the marked one? how would it be? – Marcio Lino Jun 30 '20 at 23:59
@user1460038 To get the keys before a particular key, you can modify the `getKeys` function a bit. I've added the `getBeforeKeys` function in the answer. – rishabh0211 Jul 01 '20 at 07:44
In the case, if I need to retrieve both key and value to separate arrays I would need to create another array like "values[];" and use values.push(key)? That's correct? – Marcio Lino Jul 01 '20 at 11:57
In the case, if I need to retrieve both key and value to separate arrays? I have tried like this ` for (var [key, value] of map) {console.log(key + " = " + value); ` but doesn't work – Marcio Lino Jul 01 '20 at 12:12
@user1460038 The way you mentioned above is correct if you want to access both keys and values. Destructure it by `for(var [key, value] of map)` and use key and value in the loop. – rishabh0211 Jul 01 '20 at 12:22
Yeap, work flawlessly. Thank you so much for your help. – Marcio Lino Jul 01 '20 at 15:00

Barmar · Answer 2 · 2020-06-30T21:42:53.203

0

Use Object.keys() to get the keys of an obect as an array. Then you can use indexOf() to get the index of a specific property, and you can slice the rest of the keys.

var nominalVars = {
  state: 'State',
  messoreg: 'Messoreg',
  reggeoint: 'RegGeoInt',
  reggeoimd: 'RegGeoImed',
  microreg: 'Microreg',
  regmetro: 'RegMetro',
  city: 'City',
  tipdepe: 'TipDep',
  nvldepe: 'NvlDepe',
  prefix: 'Prefix',
  subord: 'Subord'
};
let last_checkbox = "city";
let keys = Object.keys(nominalVars);
let index = keys.indexOf(last_checkbox);
let following_keys = keys.slice(index+1);
console.log(following_keys);

Note that only ES6 requires that the order of object properties to be maintained:

Does ES6 introduce a well-defined order of enumeration for object properties?

edited Jun 30 '20 at 21:42

answered Jun 30 '20 at 20:06

Barmar

741,623
53
500
612

I tried your suggestion here. It seems it only will work if I select the last option, in this case, state. If I choose [city] option, for example, the code bring me all the items above it, such as [regmetro], [microreg], and so on up to [state] option. I need to get only the option bellow city, such as [tipdepe], [nvldepe], [prefix] and [subord]. – Marcio Lino Jun 30 '20 at 21:34
I changed my snippet to use `city`, it returns `[ "tipdepe", "nvldepe", "prefix", "subord" ]` – Barmar Jun 30 '20 at 21:43
JavaScript doesn't require that `Object.keys()` return the keys in the same order that you defined them. You should use the array or `Map` solution. – Barmar Jun 30 '20 at 21:47

score 0 · Answer 3 · answered Jun 30 '20 at 20:07

0

Object.keys(obj)

Will return the defined keys for any javascript-object. You'll have to filter this array accordingly to match your requirements.

answered Jun 30 '20 at 20:07

genius42

243
1
6

Get properties in Javascript Object

3 Answers3