css：
html,body {
margin: 0;
padding: 0;
}
canvas {
margin: 0;
padding: 0;
}
html：
<canvas id="canvas"></canvas>
javascript：
dt = document.getElementById('canvas');
dt.width = window.innerWidth;
dt.height = window.innerHeight;
The result is like this: 
Logically shouldn’t canvas be as high as body? Why does body have 4 extra pixels?
Please tell me, thank you!
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
Add
to bodyPlease see: http://www.w3cplus.com/css/fi...