Javascript converting 2 string arrays to map

Question

I have two string arrays keys and values:

let keys = [a,b,c,d]
let values = [1,2,3,4]

How to convert them into a map?

Expected output would be:

{a: "1", b: "2", c: "3", d: "4"}

Answer 1

you can use Map in ES6

var myMap = new Map();

// setting the values
myMap.set('key1', 'value1');
myMap.set('key2', 'value2');
myMap.set('key3', 'value3');

your answer :

for (let i = 0; i < keys.length; i++) {
     myMap.set(keys[i], values[i]); 
}

Answer 2

Firstly create an object. Then loop through your array and add the keys and values to the object.

let keys = ['a','b','c','d'];
let values = [1,2,3,4];

let obj = {};

keys.forEach((key, index) => {
  obj[key] = values[index]
});

console.log(obj);

Answer 3

You can use array reduce on any of the array and use index to retrieve value from another array

let keys = ['a', 'b', 'c', 'd'];
let values = [1, 2, 3, 4];
let k = keys.reduce((acc, curr, index) => {
  acc[curr] = values[index]
  return acc;
}, {});

console.log(k)

Answer 4

First of all, you need to declare your string arrays properly.

let keys = ['a', 'b', 'c', 'd'];
let values = ['1', '2', '3', '4'];

var zip = (target, ...arr) => {
  if (target == null) throw Error('Target is undefined');
  if (arr[0] == null || arr[1] == null) throw Error('Lists must not be null');
  if (arr[0].length !== arr[1].length) throw Error('Lists must match in length');
  if (Array.isArray(target)) {
    arr[0].forEach((x, i) => target.push([arr[0][i], arr[1][i]]));
  } else if (typeof target === 'object') {
    arr[0].forEach((x, i) => target[arr[0][i]] = arr[1][i]);
  } else {
    throw Error('Unsupported target type');
  }
  return target;
}

var zipObj = (...arr) => zip.call(null, {}, ...arr);
var zipArr = (...arr) => zip.call(null, [], ...arr);

//console.log(zip({}, keys, values));
console.log(zipObj(keys, values)); // Zip object

//console.log(zip([], keys, values));
console.log(zipArr(keys, values)); // Zip array

.as-console-wrapper { top: 0; max-height: 100% !important; }

Answer 5

When using lodash this is a one-liner:

_.zipObject(keys,values)

Answer 6

This should do the trick:

let keys = ['a','b','c','d']
let values = [1,2,3,4]
let mapped = keys.reduce((accumulator, current, index) => {
    accumulator[current] = values[index];
    return accumulator;
}, {});

console.log(mapped)
// Result should be:
{a: 1, b: 2, c: 3, d: 4}

Reduce is a powerful method that can be used for all sorts of tasks.

Here we're "reducing" the given values of keys into an object where keys are the key and values are the correlating values.

The first parameter in reduce is a callback function that you need to pass along at minimum accumulator and current variables (can have different names); the other parameters are index and array which represent the current index of the iteration and the original array that is being iterated.

The second parameter is the initial value of the accumulator; by default it will be the first current value but in our case we set it to {} so we can treat it as an object.

I hope this helps!