TypeScript "nameof" Hacks

nameof-hacks.ts

// see issue: https://github.com/Microsoft/TypeScript/issues/1579

function nameOf<T>(obj: T) {
  let name: string;
  const makeCopy = (obj: any): any => {
    const copy = {};
    for (const key in obj) {
      defineProperty(copy, key, {
        get() {
          name = key;
          const value = obj[key];
          if (value && typeof value === "object") {
            return makeCopy(value);
          }
          return value;
        }
      });
    }
    return copy;
  };
  return (accessor: { (x: T): any }): string => {
    name = "";
    accessor(makeCopy(obj));
    return name;
  };
}

function pathOf<T>(obj: T) {
  let path: string[] = [];
  const makeCopy = (obj: any): any => {
    const copy = {};
    for (const key in obj) {
      defineProperty(copy, key, {
        get() {
          path.push(key);
          const value = obj[key];
          if (value && typeof value === "object") {
            return makeCopy(value);
          }
          return value;
        }
      });
    }
    return copy;
  };
  return (accessor: { (x: T): any }): string[] => {
    path = [];
    accessor(makeCopy(obj));
    return path;
  };
}


// these were tweaked from the nameof function shared by @rjamesnw here:
// https://github.com/Microsoft/TypeScript/issues/1579#issuecomment-394551591

function getKey(selector: (x?: any) => any) {
  const s = "" + selector;
  const m =
    s.match(/return\s+([A-Z$_.]+)/i) ||
    s.match(/.*?(?:=>|function.*?{(?!\s*return))\s*([A-Z$_.]+)/i);
  const name = (m && m[1]) || "";
  const keys = name.split(".");
  return keys[keys.length - 1];
}

function getKeyPath(selector: (x?: any) => any) {
  const s = "" + selector;
  const m =
    s.match(/return\s+([A-Z$_.]+)/i) ||
    s.match(/.*?(?:=>|function.*?{(?!\s*return))\s*([A-Z$_.]+)/i);
  const name = (m && m[1]) || "";
  const keys = name.split(".");
  return keys.slice(1);
}

omit-type.ts

// just another unrelated higher-order type that I find extremely useful

type Omit<T, K extends keyof T> = Pick<T, Diff<keyof T, K>>;