如何在 for 循环中等待响应?

2022-01-21 00:00:00 javascript ionic-framework ionic3 typescript

说明:我在for循环中调用了一个HTTP请求.我想从服务文件中获取响应然后增加循环.我如何等待从服务文件中获取响应然后执行循环.

for(let i=0;i

<块引用>

请指教

 解决方案 你应该使用异步函数.首先将 HTTP 请求转换为 Promise，然后在 for 循环中异步调用该 Promise:
 asyncReq (){return new Promise((resolve, reject) => {this.user.list_upload(JSON.stringify(ins_arr)).subscribe(data=>{if(data.hasOwnProperty('STATUS')){if(data.STATUS.toLowerCase()=='成功'){this.update();解决();}否则 if(data.STATUS.toLowerCase() == 'error'){this.user.showToast(data.MESSAGE);拒绝();}}},错误=>{this.user.showToast("服务文件出错");拒绝(错误)；});})}//异步函数，其中循环仅在 asyncReq 完成后进行异步 asyncForFunction () {for(让 i=0; i < final_arr.length; i++){等待 this.asyncReq ();}}
Description : I called an HTTP request inside for loop.I want to get the response from service file then increase loop.How can i wait to get response from service file then execute loop.
for(let i=0;i<final_arr.length;i++)
{
  this.user.list_upload(JSON.stringify(ins_arr)).subscribe(data=>{
      if(data.hasOwnProperty('STATUS'))
      {        if(data.STATUS.toLowerCase()=='success')
        {  
          this.update();
        }
        else if(data.STATUS.toLowerCase() == 'error')
        {
         this.user.showToast(data.MESSAGE);  
        }
      }
    },err=>{
      this.user.showToast("Error occurred in service file");
    });
}



  Please advise

 解决方案 You should use an async function. First convert the HTTP request to a promise, then call that promise asynchronously inside the for loop:
 asyncReq (){
    return  new Promise((resolve, reject) => {
          this.user.list_upload(JSON.stringify(ins_arr)).subscribe(data=>{
            if(data.hasOwnProperty('STATUS')){        
              if(data.STATUS.toLowerCase()=='success')
              {  
                this.update();
                resolve();
              }
              else if(data.STATUS.toLowerCase() == 'error')
              {
                this.user.showToast(data.MESSAGE);  
                reject();
              }
            }
          },err=>{
            this.user.showToast("Error occurred in service file");
            reject(err);
          });
      })
  }


  //Async function where loop progresses only after asyncReq completes
  async asyncForFunction () {
    for(let i=0; i < final_arr.length; i++){
      await this.asyncReq ();
    }
  }


	
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