Convert String Into Delimited Object Key

Question

I am trying to convert a string into a delimited object key but I need some assistance on how to iterate over the length of the array and join accordingly.

SET('my.delimited.string.of.unknown.length')

const SET = key => (state, val) => { 
        if(key.indexOf('.') !== -1) {
            let array = key.split(".")
            for (var i = 0; i < array.length; i++) {
                  // what should I do here?
            }
            // desired output based on array length
            // state[ array[0] ][ array[1] ] = val
            // state.my.delimited.string.of.unknown.length = val
        }
}

Possible duplicate of [How to set object property (of object property of..) given its string name in JavaScript?](https://stackoverflow.com/questions/13719593/how-to-set-object-property-of-object-property-of-given-its-string-name-in-ja) — Andreas, Nov 30 '18 at 18:32

score 1 · Answer 1 · answered Nov 30 '18 at 18:29

1

One of those very rare usecases for reduce:

  const keys = key.split(".");
  const prop = keys.pop();
  keys.reduce((acc, key) => acc[key], state)[prop] = val;

For sure that could also be done with a for loop:

 let array = key.split("."), acc = state;
 for (var i = 0; i < array.length - 1; i++) {
   acc = acc[ array[i] ];
 }
 acc[ array.pop() ] = val;

answered Nov 30 '18 at 18:29

Jonas Wilms

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Thanks! Not sure I fully understand whats going on here but it works. I will have to research reduce. – master00 Nov 30 '18 at 18:41
Actually, on further testing this does not work if the property contains more than 1 delimiter. – master00 Nov 30 '18 at 20:33
@master00 Add an example of that special case to the question. – Andreas Dec 01 '18 at 09:04

score 0 · Answer 2 · answered Nov 30 '18 at 18:30

For setting a value, you could split the path and reduce the path by walking the given object. If no object exist, create a new property with the name. Later assign the value.

function setValue(object, path, value) {
    var keys = path.split('.'),
        last = keys.pop();

    keys.reduce((o, k) => o[k] = o[k] || {}, object)[last] = value;
}

var test = {};
setValue(test, "first.deep.property", 1);
setValue(test, "and.another.deep.property", 20);
console.log(test);

There's an answer from you on the duplicate: https://stackoverflow.com/a/43117598/402037 — Andreas, Nov 30 '18 at 18:34

Akrion · Answer 3 · 2018-12-01T05:27:19.177

0

You could also do this with a single Array.reduce:

const makeObject = (arr, val, obj={}) => {
  arr.split('.').reduce((r,c,i,a) => r[c] = i == a.length-1 ? val : {}, obj)
  return obj
}

console.log(makeObject("first.deep.property", 1))
console.log(makeObject("and.another.deep.property", 20))

edited Dec 01 '18 at 05:27

answered Dec 01 '18 at 05:20

Akrion

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Convert String Into Delimited Object Key

3 Answers3