多级 key 的获取与赋值

deepLevelVisit.ts

type Dot = ".";
type PopFirst<K extends string> = K extends `${infer A}${Dot}${infer B}`
  ? B
  : K;
type PickFirst<K extends string> = K extends `${infer A}${Dot}${infer B}`
  ? A
  : K;

type Check<
  R,
  K extends string
> = R extends Record<string, any>
  ? PickFirst<K> extends keyof R
    ? Check<R[PickFirst<K>], PopFirst<K>>
    : undefined
  : R;

function getValue<R extends Record<string, any>, K extends string>(
  obj: R, key: K
): Check<R, K> {
  if (key === "") {
    console.error("Invalid key, the key can not be a empty string");
    // @ts-ignore
    return;
  }

  if (!key.includes(".") && Object.prototype.hasOwnProperty.call(obj, key)) {
    return obj[key];
  }

  const levels = key.split(".");
  let cur = obj;
  for (const level of levels) {
    if (Object.prototype.hasOwnProperty.call(cur, level)) {
      cur = cur[level];
    } else {
      // @ts-ignore
      return;
    }
  }

  return cur as Check<R, K>;
}

type AssignObj = Record<string | number, any>;

function setValue<Value>(obj: AssignObj, key: string, value: Value): void {
  if (key === "") {
    console.error("Invalid key, the key can not be a empty string");
    return;
  }

  if (!key.includes(".")) {
    if (Object.prototype.hasOwnProperty.call(obj, key)) {
      console.warn(`The key ${key} looks like already exists on obj.`);
    }
    obj[key] = value;
  }

  const levels = key.split(".");
  const lastKey = levels.pop()!;

  let cur = obj;
  for (const level of levels) {
    if (Object.prototype.hasOwnProperty.call(cur, level)) {
      cur = cur[level] as AssignObj;
    } else {
      console.error(
        `Cannot set value because the key ${key} is not exists on obj.`
      );
      return;
    }
  }

  if (typeof cur !== "object") {
    console.error(
      `Invalid key ${key} because the value of this key is not a object.`
    );
    return;
  }
  if (Object.prototype.hasOwnProperty.call(cur, lastKey)) {
    console.warn(`The key ${key} looks like already exists on obj.`);
  }
  cur[lastKey] = value;
}

let obj = { a: { b: "Hello", c: { D: "Hello World", E: 123 } } };

const value = getValue(obj, "a.c.E");
console.log(value);

setValue(obj, "a.d", 1234);
console.log(obj);