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

flattenObject

Flatten an object with the paths for keys.

Use recursion. Use Object.keys(obj) combined with Array.reduce() to convert every leaf node to a flattened path node. If the value of a key is an object, the function calls itself with the appropriate prefix to create the path using Object.assign(). Otherwise, it adds the appropriate prefixed key-value pair to the accumulator object. You should always omit the second argument, prefix, unless you want every key to have a prefix.

const flattenObject = (obj, prefix = '') =>
  Object.keys(obj).reduce((acc, k) => {
    const pre = prefix.length ? (prefix + '.') : '';
    if (typeof obj[k] === 'object')
      Object.assign(
        acc,
        flattenObject(obj[k], pre + k)
      );
    else acc[pre + k] = obj[k];
    return acc;
  }, {});

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