JavaScript: Unflatten an object with the paths for keys

JavaScript fundamental (ES6 Syntax): Exercise-112 with Solution

Write a JavaScript program to unflatten an object with the paths for keys.

• Use nested Array.prototype.reduce() to convert the flat path to a leaf node.
• Use String.prototype.split('.') to split each key with a dot delimiter and Array.prototype.reduce() to add objects against the keys.
• If the current accumulator already contains a value against a particular key, return its value as the next accumulator.
• Otherwise, add the appropriate key-value pair to the accumulator object and return the value as the accumulator.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const unflattenObject = obj =>
  Object.keys(obj).reduce((acc, k) => {
    if (k.indexOf('.') !== -1) {
      const keys = k.split('.');
      Object.assign(
        acc,
        JSON.parse(
          '{' +
            keys.map((v, i) => (i !== keys.length - 1 ? `"${v}":{` : `"${v}":`)).join('') +
            obj[k] +
            '}'.repeat(keys.length)
        )
      );
    } else acc[k] = obj[k];
    return acc;
  }, {});
console.log(unflattenObject({ 'a.b.c': 1, d: 1 }));

Sample Output:

{"a":{"b":{"c":1}},"d":1}

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-112-1 by w3resource (@w3resource) on CodePen.

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