原生bind、call和apply方法的实现

call 方法的实现

Function.prototype.call = function (context, ...args) {
  const ctx = context || window;
  let i = 0;
  let funcName = '';
  while(true) {
    if (!(`__CALL__${i}` in ctx)) {
      funcName = `__CALL__${i}`;
      break;
    }
    i++;
  }
  ctx[funcName] = this;
  const res = ctx[funcName](...args);

  delete ctx[funcName];
  return res;
};

apply 方法的实现

Function.prototype.apply = function (context, args) {
  const ctx = context || window;
  let i = 0;
  let funcName = '';
  while(true) {
    if (!(`__CALL__${i}` in ctx)) {
      funcName = `__CALL__${i}`;
      break;
    }
    i++;
  }
  ctx[funcName] = this;
  const res = ctx[funcName](...args);

  delete ctx[funcName];
  return res;
};

bind 方法的实现

Function.prototype.bind = function (context, ...bindArgs) {

  // 不推荐写法，不支持function属性, Date, Regexp等等，建议自己实现一个深度拷贝
  let ctx = JSON.parse(JSON.stringify(context)) || window;

  ctx.func = this;

  return function (...args) {

    bindArgs = bindArgs || [];

    args = bindArgs.concat(args);

    return ctx.func(args);

  }

}