set.ts

function shallowClone(obj: any): any {
  if (Array.isArray(obj)) {
    return obj.slice();
  }
  return Object.assign({}, obj);
}

type Path = (number | string)[];

// set is immutable object modifier
// Logic is slightly different from "lodash/set"
// it DOESNT create new path if there's none
// if path does not exist on the object, it returns the same object.
// if path resolved path field is same as input value, returns the same object.
export default function set<T>(input: T, path: Path, value: any): T {
  const newInput = shallowClone(input);
  let currentObject = newInput;
  const countTill = path.length - 1;
  for (let index = 0; index < countTill; index++) {
    const segment = path[index];
    if (!currentObject[segment]) {
      return input;
    }
    currentObject[segment] = shallowClone(currentObject[segment]);
    currentObject = currentObject[segment];
  }

  if (Object.is(currentObject[path[countTill]], value)) {
    return input;
  }

  currentObject[path[countTill]] = value;
  return newInput;
}