你的時間小時超過兩位數(shù)了

你可以檢查下，你digit文件有沒有，正不正確，如果正確就檢查下你時間是否獲取到了

我也遇到過同樣問題了，你解決了嗎

digit是數(shù)字矩陣，老師單獨(dú)定義在另外一個js文件的，你也可以在本段js中自己定義

不能讀取屬性的長度定義

var?WIDOW_WIDTH=1024;
var?WIDTH_HEIGHT=768;
var?RADIUS=8;
var?MARGIN_LEFT=30;
var?MARGIN_TOP=60;

const?endTime=new?Date(2018,4,26,17,39,56);
var?curShowTimeSeconds=0;

window.onload=function(){
	var?canvas?=document.getElementById("canvas");
	var?context?=canvas.getContext("2d");
	
	canvas.width=WIDOW_WIDTH;
	canvas.height=WIDTH_HEIGHT;
	
	curShowTimeSeconds=getCurrentShowTimeSeconds()
	
	render(context)
}

function?getCurrentShowTimeSeconds(){
	var?curTime=new?Date();
	var?ret=endTime.getTime()-curTime.getTime();
	ret=Math.round(ret/1000)
	return?ret>=0?ret:0;
}

function?render(cxt){
	
	
	var?hours=parseInt(curShowTimeSeconds/3600);
	var?minutes=parseInt((curShowTimeSeconds=hours*3600)/60);
	var?seconds=curShowTimeSeconds%60;
	
	
	renderDigit(MARGIN_LEFT,MARGIN_TOP,parseInt(hours/10),cxt);
	renderDigit(MARGIN_LEFT+15*(RADIUS+1),MARGIN_TOP,parseInt(hours%10),cxt);
	renderDigit(MARGIN_LEFT+30*(RADIUS+1),MARGIN_TOP,10,cxt);
	renderDigit(MARGIN_LEFT+39*(RADIUS+1),MARGIN_TOP,parseInt(minutes/10),cxt);
	renderDigit(MARGIN_LEFT+54*(RADIUS+1),MARGIN_TOP,parseInt(minutes%10),cxt);
	renderDigit(MARGIN_LEFT+69*(RADIUS+1),MARGIN_TOP,10,cxt);
	renderDigit(MARGIN_LEFT+78*(RADIUS+1),MARGIN_TOP,parseInt(seconds/10),cxt);
	renderDigit(MARGIN_LEFT+93*(RADIUS+1),MARGIN_TOP,parseInt(seconds%10),cxt)
}

function?renderDigit(x,y,num,cxt){
	cxt.fillStyle="black";
	for(var?i=0;i<digit[num].length;i++)
		for(var?j=0;j<digit[num][i].length;j++)
		if(digit[num][i][j]==1){
			cxt.beginPath();
			cxt.arc(x+j*2*(RADIUS+1)+(RADIUS+1),y+i*2*(RADIUS+1)+(RADIUS+1),RADIUS,0,2*Math.PI);
			cxt.closePath();
			
			cxt.fill()
		}
}

[Web瀏覽器] "Uncaught TypeError: Cannot read property 'length' of undefined" /canvas/js/countdown.js (49)