效果图

html结构

canvas31

<!DOCTYPE html>

<html>

<head>

<meta charset="utf-8">

<meta http-equiv="X-UA-Compatible" content="IE=edge">

<title>canvas31</title>

<link rel="stylesheet" href="">

</head>

<body>

<canvas id="canvas" style ="border:1px solid #aaa;diplay:block;margin:50px auto;">

当前浏览器不支持canvas,请更换浏览器后再试

</canvas>

</body>

</html>

js脚本

<script>

window.onload = function(){

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

canvas.width  = 800;

canvas.height = 800;

context = canvas.getContext("2d");

context.fillStyle = "#058";

context.font = "bold 40px sans-serif";

context.textBaseline = "top";

context.fillText("欢迎大家学习top",40,100);

drawBaseline(context,100);

context.textBaseline = "middle";

context.fillText("欢迎大家学习middle",40,200);

drawBaseline(context,200);

context.textBaseline = "bottom";

context.fillText("欢迎大家学习bottom",40,300);

drawBaseline(context,300);

context.textBaseline = "alphabetic";

context.fillText("欢迎大家学习alphabetic",40,500);

drawBaseline(context,500);

context.textBaseline = "ideographic";

context.fillText("欢迎大家学习ideographic",40,600);

drawBaseline(context,600);

context.textBaseline = "hanging";

context.fillText("欢迎大家学习hanging",40,700);

drawBaseline(context,700);

}

function drawBaseline(context,h){

var width = context.canvas.width;

context.save();

context.strokeStyle = "#888";

context.lineWidth = 2;

context.moveTo(0,h);

context.lineTo(width,h);

context.stroke();

context.restore();

}

</script>