Converting An Array To An Object

I am trying to write a function which takes in an array of arrays, and returns an object with each pair of elements in the array as a key-value pair. I have searched stack overflow

Solution 1:

Your code has several issues.

• The target object is reset to {} in each iteration. So you should move var object = {} out of your loop.

• You return from inside your loop, which immediately ends it: that should happen after the loop.

• You iterate one time too few. Remove the - 1:

  for (var i = 0; i < array.length; ++i) {
  

• There is an assignment to a numerical property, which you delete 2 lines later: that is a costly operation, which you should avoid. Just do the assignment in one operation:

  object[newArray[0]] = newArray[1];
  

Here is everything corrected:

var array = [['make', 'Ford'], ['model', 'Mustang'], ['year', 1964]];

functionfromListToObject() {
  var object = {}; // out of the loopfor (var i = 0; i < array.length; ++i) { // iterate to lastvar newArray = array[i];
    object[newArray[0]] = newArray[1];
  }
  return object; // out of the loop
}

var obj = fromListToObject(array);

console.log(obj);

ES6 Version

If you can use ES6 syntax, then consider this solution:

functionfromListToObject(array) {
    returnObject.assign(...array.map( ([key,val]) => ({[key]: val}),{}));
}

const array = [['make', 'Ford'], ['model', 'Mustang'], ['year', 1964]];
const obj = fromListToObject(array);
console.log(obj);

Using Map

You might also be interested in the ES6 Map object, which works similarly to an object, and can be constructed from your array in the most simple way:

const mp = newMap(array);

You can then access the key values as follows:

mp.get('make') === 'Ford';

And iterate:

mp.forEach( function (val, key) {
    console.log(key, val);
});

Solution 2:

Try this

You have declared obj inside the loop. During iteration

object = Object {make: "Ford"}, i = 0

After the first iteration your function

console.log(fromListToObject(array));

is called. This is because you call the return inside the loop, this should be done outside the loop. Rewrite your code as

var array = [
    ['make', 'Ford'],
    ['model', 'Mustang'],
    ['year', 1964]
  ],
  i, j = array.length,
  object = {}

functionfromListToObject() {

  for (i = 0; i < j; i++) {
    var newArray = array[i];
    object[i] = newArray[1];
    object[newArray[0]] = object[i];
    delete object[i];
  }
  return object;
}

console.log(fromListToObject(array));

var array = [['make', 'Ford'], ['model', 'Mustang'], ['year', 1964]];

var obj = {};
array.forEach(function(data){
    obj[data[0]] = data[1]
});
console.log(obj);

Solution 3:

While: Not Counting!

object = {};
while( array[0] )object[ array[0][0] ] = array[0][1], array.shift();

will result in:

object;
>> Object { make: "Ford", model: "Mustang", year: 1964 }

array;
>> Array [ ]

This action will actually dispatch array members for patching the object! The array content will be physically dislocated to the newly declared object.