adding values from an array to object javascript

Question

I have an array.

var nestedArr =[['loop0', 0], ['loop1', 1], ['loop2', 2], ['loop3', 3], ['loop4', 4], ['loop5', 5]]

I have to get using for loop this:

var obj = { loop0: 0, loop1: 1, loop2: 2 ...};

I am trying this :

for(var j = 0; j < nestedArr.length; j++){
    obj[nestedArr[j][0]] = nestedArr[j][1]}

but I am getting values as undefined. How do I add values correctly.

Can you provide a code snippet on jsFiddle or something similar? I dont really understand your problem. — Mario Murrent
– Mario Murrent, Commented May 28, 2018 at 7:57
with a declared and initialized var obj = {}, the code works. — Nina Scholz
– Nina Scholz, Commented May 28, 2018 at 7:59

Muhammad Usman · Accepted Answer · 2018-05-28 08:00:40Z

1

Working fine for me. Just added the definition of obj

var nestedArr =[['loop0', 0], ['loop1', 1], ['loop2', 2], ['loop3', 3], ['loop4', 4], ['loop5', 5]],
     obj = {};

for(var j = 0; j < nestedArr.length; j++){

obj[nestedArr[j][0]] = nestedArr[j][1]

}

console.log(obj)

answered May 28, 2018 at 8:00

Muhammad Usman

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2 Comments

Nina Scholz Over a year ago

it does not explain why but I am getting values as undefined.

Muhammad Usman Over a year ago

because it is not giving you undefined

Saeed · Accepted Answer · 2018-05-28 08:06:31Z

1

You can use reduce function as below:

var nestedArr = [
  ['loop0', 0],
  ['loop1', 1],
  ['loop2', 2],
  ['loop3', 3],
  ['loop4', 4],
  ['loop5', 5]
];

var output = {};

nestedArr.reduce(function(itm) {
  output[itm[0]] = itm[1];

});

console.log(output);

Your loop also is correct:

var nestedArr = [
  ['loop0', 0],
  ['loop1', 1],
  ['loop2', 2],
  ['loop3', 3],
  ['loop4', 4],
  ['loop5', 5]
];

var obj = {};

for (var j = 0; j < nestedArr.length; j++) {

  obj[nestedArr[j][0]] = nestedArr[j][1]

}

console.log(obj)

edited May 28, 2018 at 8:06

answered May 28, 2018 at 7:58

Saeed

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5 Comments

CertainPerformance Over a year ago

I wasn't the downvoter, but .map is not appropriate when you aren't returning anything - use .reduce instead

Nina Scholz Over a year ago

map ... without using the result. btw the given code of op works.

Saeed Over a year ago

I change it to reduce

CertainPerformance Over a year ago

@Satpal Why forEach? If reducing an array into an object, that's exactly what reduce is for

Saeed Over a year ago

Your for loop is correct and you see it runs well. whats the problem? @blahblahvah

Matus Dubrava · Accepted Answer · 2018-05-28 08:03:29Z

0

Using Array.prototype.reduce you can do this.

var nestedArr =[['loop0', 0], ['loop1', 1], ['loop2', 2], ['loop3', 3], ['loop4', 4], ['loop5', 5]]

const res = nestedArr.reduce((acc, v) => {
  acc[v[0]] = v[1];
  return acc;
}, {});

console.log(res);

answered May 28, 2018 at 8:03

Matus Dubrava

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