代码如下所示：

//根据密码长度显示安全条
          
          
密　　码：
          
 
          
*
          
          
            弱
            中
            强
          
           使用数字，字母，下划线，长度在 6 - 20 个字符之间
            
                   
          
          
function pwStrength(pwd){
  O_color="#eeeeee";
  L_color="#FF0000";
  M_color="#FF9900";
  H_color="#33CC00";
  if (pwd==null||pwd==''){
    Lcolor=Mcolor=Hcolor=O_color;
  }else{
    S_level=checkStrong(pwd);
    switch(S_level) {
      case 0:
        Lcolor=Mcolor=Hcolor=O_color;
      case 1:
        Lcolor=L_color;
        Mcolor=Hcolor=O_color;
        break;
      case 2:
        Lcolor=Mcolor=M_color;
        Hcolor=O_color;
        break;
      default:
        Lcolor=Mcolor=Hcolor=H_color;
      }
  }
  document.getElementById("strength_L").style.background=Lcolor;
  document.getElementById("strength_M").style.background=Mcolor;
  document.getElementById("strength_H").style.background=Hcolor;
  return;
}