Javascript: turn an array of keys into an empty object?

Question

I know this is probably easier than my brain is making it, but for some reason, I can't get this right:

I have an array looks like this:

["engine", "engine.car", "engine.car.driver", 
 "engine.car.passenger", "wheels", "wheels.tires"]

I want to transform above array into this object:

{
    engine : {
        car : {
            driver : undefined,
            passenger: undefined
        }
    },
    wheels : {
        tires: undefined
    }
 }

I'm using node 8.10.0.

Does the array always come sorted? For example, are all properties relating to engine going to be next to each other like in the example or can you have ["engine","wheels","engine.car","wheels.tires",...], because the solutions to this problem can vary. — user8463863, Jul 18 '18 at 16:49
@sunil I have nothing of real value to offer as far as "where I'm stuck". I know the solution is either a recursive algorithm which I am struggling with atm, or a way to access/create a nested property on a hash given the string path of it. It seems I've been marked redundant via the second solution, so that's great! No recursion! — kamii, Jul 18 '18 at 16:58
`function transformArrayToObject ( array ) { var resultObject = {}, index, item; function _transform ( _array, tmpObject ) { if ( _array.length > 1 ) { tmpObject[_array[0]] = {}; return Object.assign(tmpObject, _transform(_array.slice(1), tmpObject[_array[0]])); } else return tmpObject[_array[0]] = void 0; } for ( index = 0; index < array.length; index += 1 ) { item = array[index].split('.'); resultObject[item[0]] = item.length > 1 ? _transform(item.slice(1), {}) : void 0; } return resultObject; }` — zhibirc, Jul 19 '18 at 07:14
Are you looking for something like - https://codepen.io/nagasai/pen/djOYjP?editors=1010 which can be achieved using forEach and split() method — Naga Sai A, Jul 19 '18 at 15:02

score -3 · Answer 1 · edited Jul 04 '19 at 19:33

-3

This is pretty straightforward with JavaScript and the eval functionality. Here is a quick example.

var arr = ["engine", "engine.car", "engine.car.driver",  "engine.car.passenger", "wheels", "wheels.tires"];
 
obj = {};
for(var i = 0; i < arr.length; i++)
 eval("obj." + arr[i] + " = {}");
  
console.log(obj);

Edit

Eval is not evil, most implementations of it are but this is a perfectly valid use of it as outlined in the comments below. If you have an issue with this answer please use the comments to let me know why so I can either update the answer or OP can get the help they need.

edited Jul 04 '19 at 19:33

halfer

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answered Jul 18 '18 at 16:55

Adam H

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using `eval` is a bad idea – Get Off My Lawn Jul 18 '18 at 16:56
@GetOffMyLawn Care to expand on that? – Adam H Jul 18 '18 at 17:20
https://stackoverflow.com/questions/86513/why-is-using-the-javascript-eval-function-a-bad-idea – Get Off My Lawn Jul 18 '18 at 17:55
@GetOffMyLawn '_Improper use of eval opens up your code for injection attacks_' this isn't data from user input so an injection attack doesn't apply here. '_Debugging can be more challenging (no line numbers, etc.)_' that's a fair argument. '_eval'd code executes slower (no opportunity to compile/cache eval'd code)_' Even it that thread he points out that isn't the issue it used to be. There are no absolutes, this is a perfectly fine use of eval. – Adam H Jul 18 '18 at 18:17
And how do you know this isn't user input? – Get Off My Lawn Jul 18 '18 at 18:23
@GetOffMyLawn because it's in an array – Adam H Jul 18 '18 at 18:24
Which could have been generated from user input... – Get Off My Lawn Jul 18 '18 at 18:27
Sure, it _could_ have but you just said 'using eval is a bad idea' you have no more information than I do so there is no way you can know if it is a 'bad idea' is all I'm saying. There are certainly valid times to use eval and this is potentially one of them. – Adam H Jul 18 '18 at 18:28

Javascript: turn an array of keys into an empty object?

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