题解 | #修改 this 指向#

手写 bind

function bindThis(f, oTarget) {
  if (typeof f !== "function") throw new TypeError(f + " must be a function");
  let o = Object(oTarget);
  let args = [].slice.call(arguments, 2);
  let bound = function (...boundArgs) {
    let finalArgs = [...args, ...boundArgs];
    if (this instanceof bound) {
      if (f.prototype) {
        bound.prototype = Object.create(f.prototype);
      }
      let res = f.apply(this, args);
      if (typeof res === "object" || typeof res === "function") {
        return res;
      }
      return this;
    } else return f.apply(o, finalArgs);
  };
  return bound;
}