Implement lodash.set(obj, path, value) — create nested path

Question

Accepted Answer

**Approach:** Split path to keys, walk/create intermediate objects or arrays (numeric key -> array). Final key set.

```javascript
function set(obj, path, value) {
  const keys = Array.isArray(path) ? path : path.replace(/$$(\w+)$$/g, '.$1').split('.').filter(Boolean);
  let cur = obj;
  for (let i=0; i<keys.length; i++) {
    const k = keys[i];
    if (i === keys.length - 1) cur[k] = value;
    else {
      if (cur[k] == null || typeof cur[k] !== 'object') {
        const nextIsIndex = /^\d+$/.test(keys[i+1]);
        cur[k] = nextIsIndex ? [] : {};
      }
      cur = cur[k];
    }
  }
  return obj;
}

// Demo
const o = {};
set(o, 'a.b[0].c', 42);
console.log(JSON.stringify(o)); // {"a":{"b":[{"c":42}]}}
console.log(set({a:{b:1}}, 'a.b', 2)); // {a:{b:2}}
console.log(set({}, ['x','y',0], 'hi')); // {x:{y:['hi']}}
console.log(set({a:[]}, 'a[1].b', 5)); // {a:[undefined,{b:5}]}
```
Companion to `get`; handle array indices by checking if next key is numeric.

Implement lodash.set(obj, path, value) — create nested path

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