Question

在ngOnInit（）mehtod中，我得到一个HTMLElement并用它来设置一个变量：

ngOnInit(){
this.popUpContainerDisplay = document.getElementById('popUpContainer');
console.log("pop", this.popUpContainerDisplay);
this.popUpAcceptContainerDisplay = document.getElementById('acceptPopUp');
this.popUpDeclineContainerDisplay = document.getElementById('declinePopUp');
this.popUpWarningContainerDisplay = document.getElementById('warningPopUp');
}


popUpFadeOut(): void{
if(this.popUpContainerDisplay.style.opacity == "0"){
console.log("fine", this.popUpContainerDisplay);
this.popUpContainerDisplay.style.opacity = "1";
this.popUpContainerDisplay.style.display = "block";

setTimeout(this.fade, 1000); //popup box fades away after 1 seconds
}
}

fade(): void {
console.log("notFine", this.popUpContainerDisplay);
this.newOpacity = parseInt(this.popUpContainerDisplay.style.opacity) - .01;
this.popUpContainerDisplay.style.opacity = String(this.newOpacity);

if (this.newOpacity <= 0)
{
this.popUpContainerDisplay.style.display = "none";
this.popUpContainerDisplay.style.opacity = "0";
}
else
{
requestAnimationFrame(this.fade);
}
}

constructor(private biddingService: BiddingService) {


biddingService.bids.subscribe(bid => {

if(bid.bidderArray){
this.bidderArray = bid.bidderArray; //.join('');
this.highestBid = bid.bid;

this.popUpContainerDisplay.style.display = bid.popUpContainerDisplay;
this.popUpContainerDisplay.style.opacity = bid.popUpContainerOpacity;  

this.popUpAcceptContainerDisplay = bid.popUpAcceptContainerDisplay;
this.popUpDeclineContainerDisplay = bid.popUpDeclineContainerDisplay;
this.popUpWarningContainerDisplay = bid.popUpWarningContainerDisplay;
this.arrayReset = bid.resetArrayBoolean;
this.popUpFadeOut();
}


});
}

ngOnInit（）和popUpFadeOut（）在控制台中记录元素，但fade（）记录'undefined'。为什么元素突然未定义？

Answer 1

您可以使用箭头功能确保this方法中的上下文fade成为您组件的实例：

setTimeout(() => this.fade(), 1000);

或

fade = () => {
  console.log("notFine", this.popUpContainerDisplay);
  this.newOpacity = parseInt(this.popUpContainerDisplay.style.opacity) - .01;

另请参阅此处的其他选项：

Angular2 injected Router is undefined

HTMLElement突然未定义

1 个答案: