30-seconds-of-code/snippets/unflattenObject.md

title, tags

title	tags
unflattenObject	object,advanced

Unflatten an object with the paths for keys.

Use Object.keys(obj) combined with Array.prototype.reduce() to convert flattened path node to a leaf node. If the value of a key contains a dot delimiter (.), use Array.prototype.split('.'), string transformations and JSON.parse() to create an object, then Object.assign() to create the leaf node. Otherwise, add the appropriate key-value pair to the accumulator object.

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;
  }, {});

unflattenObject({ 'a.b.c': 1, d: 1 }); // { a: { b: { c: 1 } }, d: 1 }