Javascript: email address field validation

Use the following code

function EmailIdCheck(str) {

var at=”@”
var dot=”.”
var lat=str.indexOf(at)
var lstr=str.length
var ldot=str.indexOf(dot)
if (str.indexOf(at)==-1){
alert(“Please enter a valid email address”)
return false
}

if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
alert(“Please enter a valid email address”)
return false
}

if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
alert(“Please enter a valid email address”)
return false
}

if (str.indexOf(at,(lat+1))!=-1){
alert(“Please enter a valid email address”)
return false
}

if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
alert(“Please enter a valid email address”)
return false
}

if (str.indexOf(dot,(lat+2))==-1){
alert(“Please enter a valid email address”)
return false
}

if (str.indexOf(” “)!=-1){
alert(“Please enter a valid email address”)
return false
}

return true
}

function ValidateForm() {
var emailID = document.getElementById(“TextBox1″).value

if ((emailID == null)||(emailID == “”)){
alert(“Please Enter your Email ID”)
emailID.focus()
return false
}
if (EmailIdCheck(emailID) == false) {
emailID=”"
document.getElementById(“TextBox1″).focus()
return false
}
return true
}

In HTML body tag call this function

Button ID=”Button1″ runat=”server” Text=”Button” OnClientClick=”return ValidateForm()”

Thanks,
Anil.