? window.onload = function(){

??????? var canvas = document.getElementById("canvas");

??????? canvas.width = 800;
??????? canvas.height = 800;

??????? var cxt=canvas.getContext('2d');
??????? cxt.moveTo(10,10);
??????? cxt.lineTo(100,400);
??????? cxt.lineWidth=3;
??????? cxt.strokeStyle="rgba(0,0,0,0.5)";
??????? cxt.stroke();

??? }