CODEWITHSUNDEEP
javascriptnode.jsecmascript-6es6-class
Kunal Vashist
Kunal Vashist

Reputation: 2471

How to get Map as an object in javascript ES6?

My Class is using es6 to create an map object at node level, using Map()--"set" function.When class is called i want the map object to get converted to normal json type structure. I am using moongoose to retreive the data from database.

res.json(MapObject);

After using this res.json whole content inside parent node is getting empty.

{success:{},
 error:{},
redirectMe:false}

Have Map Object like this

{
  success: 
   Map {
     'String1' => 'true',
     'Object1' => [ [Object],
                    [Object],
                    [Object],
                    [Object],
                    [Object]
                  ]
     'String2' => 100 
     }
  error: Map {},
  redirectMe: false 
}

I want to get result as an Object but when I tries to get it not able to get anything

Wanted something like

{
  success: 
    {
     'String1' : 'true',
     'Object1' : [ [Object],
                    [Object],
                    [Object],
                    [Object],
                    [Object]
                  ]
     'String2' : 100 
     }
  error: {},
  redirectMe: false 
}

Upvotes: 18

Views: 16974

Answers (4)

T.J. Crowder
T.J. Crowder

Reputation: 1074495

Now that JavaScript has Object.fromEntries (added in ES2019, easily polyfilled), this is a one-liner:

const obj = Object.fromEntries(map);

Live Example:

const map = new Map();
map.set("string1", true);
map.set("someArray", [{a:1}, {b:2}, {c:3}]);
map.set("string2", 100);

const obj = Object.fromEntries(map);

console.log(obj);
.as-console-wrapper {
  max-height: 100% !important;
}

The Map's keys must be strings or Symbols, or things that can be meaningfully converted to strings, since property keys in objects can only be strings or Symbols.

Previous answer: If you have a Map and you want to convert it to a plain object, that's easily done if the Map's keys are strings or Symbols or something (numbers, for instance) that can meaningfully be converted to strings.

You just loop over its keys:

const obj = {};
for (const key of map.keys()) {
  obj[key] = map.get(key);
}

Live Example:

const map = new Map();
map.set("string1", true);
map.set("someArray", [{a:1}, {b:2}, {c:3}]);
map.set("string2", 100);

const obj = {};
for (const key of map.keys()) {
  obj[key] = map.get(key);
}

console.log(obj);
.as-console-wrapper {
  max-height: 100% !important;
}

That said, as Kunal noted, it might make more sense to use entries (and you don't need .entries(), you can just use of map to get the default iterator, which is for entries).

Upvotes: 13

Emad Salah
Emad Salah

Reputation: 845

You can convert a map to an object easily using a native JS function:

Object.fromEntries(map);

Note: This function is part of the ECMAScript 10 spec and is supported by Node.js 12+ and Chrome 73+, could also be polyfilled to work on older platforms using this plugin

const map = new Map();
// Setting up some sample data
map.set("foo", "bar");
map.set("pets", ["Fido", "Foobar", "Al"]);
// Convert map to object
const convertedMap = Object.fromEntries(map);

console.log(convertedMap);

Upvotes: 22

Vladimir Goldobin
Vladimir Goldobin

Reputation: 246

One-liner to convert Map to plain Object:

Object.assign({}, ...[...m.entries()].map(([k, v]) => ({[k]: v})))

Upvotes: 4

Kunal Vashist
Kunal Vashist

Reputation: 2471

Better way to convert map to object 

let jsonResponse = {};
            for(let [key,val] of MapObject.entries()){
                jsonResponse[key]= val;
            }

console.log(jsonResponse);

Upvotes: 2

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