即使在向其中推入元素后，数组元素仍未定义

Question

我正在构建视频保存服务作为项目，并从数据库response.array[]获得用户保存的视频数组，然后将videoId推入显示阵列video[]，但在显示各自videoId使用console.log()它不断未定义。

我有如下的代码片段。

let video = []; 
this.service.nextVideo().subscribe(response => 
{ 
    response.array.forEach(element => { 
    video.push(element.videoId); 
    }); 
}) 
console.log(video[0]); //Output is undefined 

完整的代码片段就像这样

nxtVideo(){ 
    let video = []; 
    this.service.nextVideo().subscribe(response => 
    { 
     response.array.forEach(element => { 
      console.log(element.videoId);//Display's video id 
      video.push(element.videoId); 
     }); 
    }) 
    console.log(video[0]); //Output undefined 
    console.log(video); //Output shows all elements but on accessing specific elements it shows undefined 
    return (video[this.offset++]); //offset is a global variable to measure watched videos 
    } 

    Launch(){ 
    let videoId = this.nxtVideo(); 
    //The Display table starts here 
    } 

Answer 1

试试这个代码。它必须是工作，因为它的异步功能。

let video = []; 
this.service.nextVideo().subscribe(response => 
{ 
    response.array.forEach(element => { 
     video.push(element.videoId); 
    }); 
    console.log(video[0]); //Output is undefined 
})