<html><body><p>单击该按钮以显示格式化的数字。</p><button onclick="myFunction()">试一试</button><p id="demo"></p><script>function myFunction() { var num = 0.001658853; var a = num.toPrecision(); var b = num.toPrecision(2); var c = num.toPrecision(3); var d = num.toPrecision(10); var n = a + "<br>" + b + "<br>" + c + "<br>" + d; document.getElementById("demo").innerHTML=n;}</script></body></html>