Question

我想在每次api调用后设置一些等待时间。因此，我为调用for循环的api添加了setTimeout，但它提供了setTimeout中未定义的createAPIService的api服务。下面是我的代码。

for (let i = 0; i < this.fooditemselecteddetails.length; i++) {
  this.spinnerService.hide();
  setTimeout(function() {
    this.common.createAPIService('api/booking/AddConcessions?CinemaId=' + this.cinemaid + '&TransactionId=' + this.temptransaction.TransactionId + '&ItemId=' + this.fooditemselecteddetails[i].id + '&Quantity=' + this.fooditemselecteddetails[i].quantity + "&BookingId=" + this.transactionAPIRequest.ORDER_ID, '')
  .subscribe((result: any) => {

      this.spinnerService.hide();
      this.addconcession = result;
      console.log(this.addconcession);


      if (this.addconcession.IsSuccess == true) {

        if (i == this.fooditemselecteddetails.length - 1) {
          localStorage.setItem("bookingid", this.transactionAPIRequest.ORDER_ID);
          this.common.createAPIService('api/booking/FinalBookingDetails?BookingId=' + this.transactionAPIRequest.ORDER_ID, '').subscribe((result2: any) => {
            this.vistavalidation = result2;
            if (this.vistavalidation.BookingID > 0) {
              this.common.createAPIService('api/booking/ContinueTransaction?CinemaId=' + this.cinemaid + '&TransactionId=' + this.temptransaction.TransactionId, '').subscribe((result3: any) => {
                if (result3.IsSuccess) {
                  this.ContinueTransactionresult = result3;
                  this.showTabOnClick('tabs-4');
                } else {
                  this.common.ShowNotification("Food Item", result3.Error, "info");
                  this.spinnerService.hide();
                }
              });
            } else {

              this.common.ShowNotification("Food Item", 'something went wrong, please try again', "info");
              this.spinnerService.hide();
            }
          });
        }
      } else {
        this.common.ShowNotification("Food Item", result.Error, "error");
        this.spinnerService.hide();

      }
    });
  }, 2000);

  console.log(this.addconcession);

}

Answer 1

尝试使用箭头函数语法保留 this

的范围

setTimeout(() => { 代替 setTimeout(function() => { ：

for (let i = 0; i < this.fooditemselecteddetails.length; i++) {
  this.spinnerService.hide();
  setTimeout(() => { ... }, 2000);

  console.log(this.addconcession);

}

Answer 2

使用箭头功能，即setTimeout(()=>{ },1000)。它将继承父级的this，您将可以使用this访问类的所有方法和变量。

Answer 3

将此“ s etTimeout（function（）{”）替换为“ setTimeout（（）=> {””。

Answer 4

使用箭头功能时，将创建一个闭合。闭包是一个内部函数，可以访问外部（封装）函数的变量-作用域链。闭包具有三个作用域链：它可以访问自己的范围（在大括号之间定义的变量），可以访问外部函数的变量，并且可以访问全局变量。

此处有更多详细信息：http://javascriptissexy.com/understand-javascript-closures-with-ease/

setTimeout中的函数给出未定义

4 个答案: