How to convert function arguments into key/value pair?

Question

I'm trying to find a way to make the following possible with NodeJS.

a = 10
b = 20
c = 30
d = 40
......
......

function getObject(a, b, c, d, ....) => {

    // this function should return an object.
    // return {
          a : 10,
          b : 20,
          c : 30,
          d : 40,
          .......
          .......
        }
   }

Is there a way to do it in javascript (NodeJS)?

[Edit - Solved]

As suggested by @Offirmo in this thread and @MarkMeyer in the comments, the problem in the question can be solved with ES6 object notation.

let a = 10;
let b = 20;

function getOject(data){
    console.log(data)
}

getObject({a,b}) // { a: 10, b: 20 }

The function will be called with n number or arguments (variables). `getObject(a, b, c, d, ......)` — Joy, Aug 26 '18 at 01:51
So if you can have code that calls `obj = getObject(a, b, c, d, ......)` why don't you just use `obj = {a, c, b, d}` and make the object that way? Why do you need a function? — Mark, Aug 26 '18 at 01:53
So basically I want something like, nameOfVariable : valueOfVariable pair. — Joy, Aug 26 '18 at 01:54
Instead of creating the object manually for n-number of variables, I want to generate it dynamically by just using the variable. — Joy, Aug 26 '18 at 01:56
Oh! never mind, I see what you are saying. Wow! never thought it's that easy. — Joy, Aug 26 '18 at 01:58
In that case this question is a dupe of: https://stackoverflow.com/questions/3404057/determine-original-name-of-variable-after-its-passed-to-a-function and @MarkMeyer's solution is a dupe of @ Offirmo's solution there — duhaime, Aug 26 '18 at 01:59
@duhaime, Thanks for pointing that out, that question didn't pop up for my search queries. — Joy, Aug 26 '18 at 02:03

colxi · Answer 1 · 2018-08-26T02:20:59.950

Solution 1:

It should be as simple as this :

function test(a,b,c,d){
  return {a,b,c,d}
}

let result= test(1,2,3,4)
console.log(result)

Solution 2:

Generic Method for getting the parameters object, in any function... Should work ... but it uses arguments.callee which is deprecated since ECMAScript 5 ( however it still does work in most major browsers.)

function getArgumentsObject(fn,arg){
  let STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;
  let ARGUMENT_NAMES = /([^\s,]+)/g;  
  let fnStr = fn.toString().replace(STRIP_COMMENTS, '');
  let names = fnStr.slice(fnStr.indexOf('(')+1, fnStr.indexOf(')')).match(ARGUMENT_NAMES);
  if(names === null) na,es = [];
     
  let obj = {};
  for(let a=0; a<Array.from(arg).length; a++){
    obj[names[a]]=arg[a]
  }
  return obj;
}

function test(a,b,c,d){
  return getArgumentsObject(arguments.callee, arguments);
}

let result = test(1,2,3,4)
console.log(result)

Joy · Accepted Answer · 2018-08-26T02:18:17.900

1

As suggested by @Offirmo in this thread and @MarkMeyer in the comments, the problem in the question can be solved with ES6 object notation.

let a = 10;
let b = 20;

function getOject(data){
     console.log(data)
}

getObject({a,b}) // { a: 10, b: 20 }

edited Aug 26 '18 at 02:18

answered Aug 26 '18 at 02:08

Joy

45
1
9

Mke Spa Guy · Answer 3 · 2018-08-26T02:19:56.793

1

Nope, once you pass the values to a function, the function can not access the variable names. Keep in mind, a value may be passed directly without a variable name.

const getObject = (a, b, c, d) => ({a, b, c, d})
const foo = 1;
const obj = getObject(foo, 2, 3, 4};
console.log(obj); // {a: 1, b: 2, c: 3 d: 4}

In es6+ you can create a new object like this Mark Meyer states:

const obj = {a, b, c, d};

edited Aug 26 '18 at 02:19

answered Aug 26 '18 at 02:08

Mke Spa Guy

793
4
13

score 0 · Answer 4 · answered Aug 26 '18 at 03:36

I propose to make use of the arguments object. We convert arguments to an array, and then we build an Object, based on the output. To get keys in alphabetic order, we'd use String.fromCharCode().

const foo = function() {
  const _args = [].slice.call(arguments).reduce((obj, key, index) => ({
    ...obj,
    [String.fromCharCode(97 + index)]: arguments[index]
  }), {})

  return _args // { a: 1, b: "hello", c: 2, d: 3, e: "world" }
}

foo(1, 'hello', 2, 3, 'world')

How to convert function arguments into key/value pair?

4 Answers4

Solution 1:

Solution 2: