為什么一模一樣的代碼，我自己敲一遍，就運行不出來相同的效果？

var WINDOW_WIDTH=1024;

var WINDOW_HEIGHT=768;

var WINDOW_TOP=60;

var WINDOW_LEFT=30;

var RADIUS=10;

?

window.onload = function () {

??? var canvas=document.getElementsById('canvas');? ??//調用canvas

??? var context=canvas.getContext("2d");?? //調用繪圖的上下文環(huán)境

?

??? canvas.width=WINDOW_WIDTH;

??? canvas.height=WINDOW_HEIGHT;? //調用全局變量

?

??? render(context)?? //繪圖函數

};

?

function render(cxt) {

??? var hours=12;

??? var minutes=34;

??? var seconds=56;?? //定義時間

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??? renderDigit(WINDOW_LEFT,WINDOW_TOP,parseInt(hours/10),cxt);? //將數拆開，一個數一個數的繪制

??? renderDigit(WINDOW_LEFT+15*(RADIUS+1),WINDOW_TOP,parseInt(hours%10),cxt);

??? renderDigit(WINDOW_LEFT+30*(RADIUS+1),WINDOW_TOP,10,cxt);

??? renderDigit(WINDOW_LEFT+39*(RADIUS+1),WINDOW_TOP,parseInt(minutes/10),cxt);

??? renderDigit(WINDOW_LEFT+54*(RADIUS+1),WINDOW_TOP,parseInt(minutes%10),cxt);

??? renderDigit(WINDOW_LEFT+69*(RADIUS+1),WINDOW_TOP,10,cxt);

??? renderDigit(WINDOW_LEFT+78*(RADIUS+1),WINDOW_TOP,parseInt(seconds/10),cxt);

??? renderDigit(WINDOW_LEFT+93*(RADIUS+1),WINDOW_TOP,parseInt(seconds%10),cxt);

}

?

function renderDigit(x,y,num,cxt){

??? cxt.fillStyle="rag(0,102,153)";

???

??? for(var i=0;i<digit[num].length;i++)?? //i代表行，j代表列，num代表數，.length代表方法

??????? for(var j=0;j<digit[num][i].length;j++)???? //1是矩陣里的，代表繪制小球

??????? {

??????????? if(digit[num][i][j] == 1) {

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??????????????? cxt.beginPath();? //繪圖的一個區(qū)間

??????????????? 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()

??????????? }

??????? }

}

這有什么錯誤？為什么運行不了？