<!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"> <title>计算1到100的和</title> </head> <script type="text/javascript"> function sum1(){ var a=document.getElementById("m1"); a=parseInt(a.value); var b=document.getElementById("n1"); b=parseInt(b.value); var s=0; for(var i=a;i<=b;i++){ s+=i; } alert(s); } function sum2(){ var a=document.getElementById("m1"); a=parseInt(a.value); var b=document.getElementById("n1"); b=parseInt(b.value); var s=0; var i=a; do{ s+=i; i++; }while(i<=b) alert(s); } function sum3(){ var a=document.getElementById("m1"); a=parseInt(a.value); var b=document.getElementById("n1"); b=parseInt(b.value); var s=0; var i=a; while(i<=b){ s+=i; i++; } alert(s); } </script> <body> 计算从<input id="m1" type="text">到<input id="n1" type="text">的值 <button onclick="sum1()">用for循环计算</button> <button onclick="sum2()">用do...while循环计算</button> <button onclick="sum3()">用while循环计算</button> </body> </html>