how do I convert an object to an array list in JS

Question

I have a problem with my code it has a running error I am trying to convert an object to an array list. In my code, I was trying to build an array inside an array! I was expecting to have a return value as the following:

[['name', 'Holly'], ['age' , 35], ['role', 'producer' ],

['species', 'canine'], ['name', 'Bowser'], ['weight', 45]]

I will appreciate any help or advice thanks.

var obj1 = {
  name: 'Holly',
  age: 35,
  role: 'producer'
};
var obj2 = {
  species: 'canine',
  name: 'Bowser',
  weight: '45'
};

function convertObjectToList(obj) {
  var arrayExt = []; // declare my external array container
  var arrayInt = []; // declare my internal arrays container
  var objKeys = Object.getOwnPropertyNames(obj); // returns all properties (enumerable or not) found directly upon a given object. 
  for (var k in obj) {
    if (var i = 0; i < objKeys.length; i++);
    arrayInt = [];
    arrayInt.push(obj(objKeys[k]));
    arrayExt.push(arrayInt);
    console.log(arrayExt);
  }
}
convertObjectToList(obj);

It sounds like you want Object.entries. It has low browser support, but there are polyfills. — castletheperson
– castletheperson, Commented Jul 14, 2017 at 0:12
What is if (var i = 0; i < objKeys.length; i++); supposed to be? You're mixing up if and for syntax. — Barmar
– Barmar, Commented Jul 14, 2017 at 0:42

Fabien · Accepted Answer · 2017-07-14 00:20:45Z

3

This should do the trick?

    var obj1 = { name: 'Holly', age: 35, role: 'producer' };
    var obj2 = { species: 'canine', name: 'Bowser', weight: '45'};

    function convertObj(obj) {
        var result = [];
        for (var key in obj) {
            result.push([key, obj[key]])
        }
        return result;
    }
    
    console.log(convertObj(obj1))
    console.log(convertObj(obj2))

Gives (NodeJS):

> convertObj(obj1)
[ [ 'name', 'Holly' ],
  [ 'age', 35 ],
  [ 'role', 'producer' ] ]

edited Jul 14, 2017 at 0:20

answered Jul 14, 2017 at 0:13

Fabien

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Comments

m0meni · Accepted Answer · 2017-07-14 01:01:40Z

1

You can just use a use a combination of Object.keys, Array.map, and Array.concat

function toArray(obj) {
  return Object.keys(obj).map(k => [k, obj[k]]);
}

var obj1 = { name: 'Holly', age: 35, role: 'producer' };
var obj2 = { species: 'canine', name: 'Bowser', weight: '45'};

console.log(toArray(obj1).concat(toArray(obj2)))

In general, you should avoid for...in loops. There are many better alternatives now.

edited Jul 14, 2017 at 1:01

answered Jul 14, 2017 at 0:51

m0meni

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2 Comments

Salma Elshahawy Over a year ago

Thanks@AR7 really helped me

m0meni Over a year ago

@Salma let me know if you have any followup questions or if anything wasn't clear

Rick · Accepted Answer · 2017-07-14 00:37:20Z

1

With ECMAScript2017 you can use Object.entries or a traditional "for in" loop

var obj1 = {
  name: 'Holly',
  age: 35,
  role: 'producer'
};
var obj2 = {
  species: 'canine',
  name: 'Bowser',
  weight: '45'
};



var arr1 = Object.entries(obj1)

console.log(arr1);

var arr2 = Object.entries(obj2)

console.log(arr2);



//traditional for in loop

var tr1 = [];
for (let iter in obj1) {
  tr1.push([iter, obj1[iter]])

}

console.log(tr1);

var tr2 = [];
for (let iter in obj2) {
  tr2.push([iter, obj2[iter]])

}
console.log(tr2);

edited Jul 14, 2017 at 0:37

answered Jul 14, 2017 at 0:11

Rick

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5 Comments

Fabien Over a year ago

NodeJS: TypeError: Object function Object() { [native code] } has no method 'entries'

Rick Over a year ago

@Fabien upgrade your version of Node

Fabien Over a year ago

Damned, maybe :-D Another approach is to use Object.keys(a).map(function(keyName, keyIndex) { ...

Salma Elshahawy Over a year ago

this gives the result but gives an undefined

Rick Over a year ago

@salma what can you explain what you mean by undefined? are you getting this in Node?

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