你的时间小时超过两位数了

你可以检查下，你digit文件有没有，正不正确，如果正确就检查下你时间是否获取到了

我也遇到过同样问题了，你解决了吗

digit是数字矩阵，老师单独定义在另外一个js文件的，你也可以在本段js中自己定义

不能读取属性的长度定义

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浏览器] "Uncaught TypeError: Cannot read property 'length' of undefined" /canvas/js/countdown.js (49)