javascript密码强度提示

%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="PasswordStrong._Default" %

!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"

html xmlns="http://www.w3.org/1999/xhtml"
head runat="server"
    title/title
/head
body
    form id="form1" runat="server"
    div
    input  id="reg_passwd__" name="reg_passwd__" value="" ;="" onkeyup="update_strength('reg_passwd__','reg_passwd__strength_display__')" autocomplete="off" type="password"/
    script type="text/javascript"
   function update_strength(input_field_id, output_display_id)
    {
    var input_field = document.getElementById(input_field_id);
    var output_display = document.getElementById(output_display_id);
       
    var input_str = input_field.value;
    var input_length = input_str.length;

    var strength = 0;

    // increase strength if contains [0-9]
    number_re = new RegExp("[0-9]");
    if (number_re.test(input_str)) {
      strength++;
    }
    // increase strength if contains non alpha
    non_alpha_re = new RegExp("[^A-Za-z0-9]");
    if (non_alpha_re.test(input_str)) {
      strength++;
    }

    // increase strength if contains upper case
    upper_alpha_re = new RegExp("[A-Z]");
    if (upper_alpha_re.test(input_str)) {
      strength++;
    }
   
    // increase strength if long enough
    if(input_length =8) {
      strength++;
    }   

    var strength_str;
    if (strength = 1) {
        strength_str = 'strong style="color:blue"弱/strong';
    } else if (strength = 2) {
      strength_str = 'strong style="color:blue"中等/strong';
    } else {
      strength_str = 'strong style="color:green"强壮/strong';
    }
   
    if(input_str.length 6) {
      strength_str = 'strong style="color:orange"太弱/strong';
    }

    output_display.innerHTML  = strength_str;
}
/script
div
span密码强度: /span
span id="reg_passwd__strength_display__"
/span
/div
    /div
    /form
/body
/html