Create a JSON object using an array of nodes - node.js

Question

I the results of a table that gives me the dynamic hierarchy of fields that i am needing to use to create a JSON object from.
EX:
[ [ 'request', 'cycleRange' ],
[ 'request', 'cycleRange', 'from' ],
[ 'request', 'cycleRange', 'to' ],
[ 'request', 'cycleRange', 'to', 'month' ],
[ 'request', 'cycleRange', 'to', 'year' ],
[ 'request', 'datestmt' ],
[ 'request', 'singleTran' ],
[ 'request', 'singleTran', 'datePost' ],
[ 'request', 'singleTran', 'dateTo' ] ]
The JSON object i am expecting to create with this sample should be:
let expected = {
request: {
cycleRange: {
from: null,
to: {
month: null,
year: null
}
},
datestmt: null,
singleTran: {
datePost: null,
dateTo: null
}
}
};
I am using this function to try and build the object, but i am only getting the final array as the object:
let final = {};
for (let i of heirarchy) {
assign(final, i, null);
}
function assign(obj, keyPath, value) {
let lastKeyIndex = keyPath.length - 1;
let key;
let i;
for (i=0; i<lastKeyIndex; i++) {
key = keyPath[i];
if (!(key in obj)) {
obj[key] = {};
} else {
if (i !== lastKeyIndex) {
obj[key] = {};
}
}
obj = obj[key];
}
obj[keyPath[lastKeyIndex]] = value;
}
Currently my results i am only getting: (the last index of my source hierarchy)
{"request":{"singleTran":{"dateTo":null}}}
Any help would be appreciated.

Answer 1

because obj is referencing final, this line is likely causing you mischief:
obj = obj[key];
This will overwrite the obj (in this case final) every iteration of hte loop. I would recommend keeping track of a separate variable so that final remains un-mutated

Answer 2

I have this solution but I think there is a lot of room for simplification and improvement, also I replaced null by {}.
You could use _.set from lodash: https://lodash.com/docs/4.17.11#set to replace set in my example.
const array = [ [ 'request', 'cycleRange' ],
[ 'request', 'cycleRange', 'from' ],
[ 'request', 'cycleRange', 'to' ],
[ 'request', 'cycleRange', 'to', 'month' ],
[ 'request', 'cycleRange', 'to', 'year' ],
[ 'request', 'datestmt' ],
[ 'request', 'singleTran' ],
[ 'request', 'singleTran', 'datePost' ],
[ 'request', 'singleTran', 'dateTo' ] ];
const set = (path, obj) => path.split('.').reduce((o,i)=> {
return o[i] ? o[i] : o[i] = {};
}, obj)
let myNewObject = {};
let path = '';
array.forEach(element => {
path = '';
element.forEach(key => {
path = path ? path + '.' + key : key;
set(path, myNewObject);
});
});
console.log(myNewObject);

Answer 3

I wound up using package deepmerge to merge the individual results into my final object
const deepmerge = require('deepmerge');
let final = {};
for (let i of heirarchy) {
let temp = {};
assign(temp, i, null);
final = deepmerge(final, temp);
}