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<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title></title> </head> <body> <canvas id="canvas" width="400" height="400" style="background:gray;"></canvas> <script> var canvas = document.getElementById(‘canvas‘) var context = canvas.getContext(‘2d‘) var lastTime = 0 function calculateFPS() { var now = +new Date() var fps = 1000 / (now - lastTime) lastTime = now return fps } function animate() { context.clearRect(0, 0, canvas.width, canvas.height) context.font = ‘38px arial‘ context.fillText(calculateFPS().toFixed() + ‘ fps‘, 45, 50) window.requestAnimationFrame(animate) } window.requestAnimationFrame(animate) </script> </body> </html>
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原文地址：http://www.cnblogs.com/jzm17173/p/4191956.html
