Javascript正则表达式来检测一个字符串是否有两个“ @”字符？

Question

I am trying to do a simple verification that a string contains only one email address. I am guessing that the easiest way to do this is to look for duplicate "@" chars and reject if that is the case. I have this code, and I tested the regex on regex101 and it worked perfectly. But I'm getting nothing from this now that it's in the page:

function checkemail(input){
var validformat=/^.*@.*@+.*?/
var returnval=false
if (!validformat.test(input.value))
alert("Invalid email format. Please correct and submit again.")
else{ returnval=true
}
if (returnval==false) input.select()
return returnval
}

And I am calling this with:

<form action="storemessage.php" method="POST" onSubmit="return checkemail(this.recipemail)">

And the name of the field is "recipemail." Stumped. Hoping this is something simple that I've just not had enough coffee to see...

Answer 1

Regex test returns true if the string matches the format (in your case, if it contains @x2). So you want to change your if condition to act on true values, not false:

if (validformat.test(input.value)) {
    alert("Invalid email format. Please correct and submit again.");
}

And perhaps you should rename your regex to invalidformat .

Answer 2

Validating emails in JS is a very tedious task, there are hundreds of weird scenarios you could account for, but it's simply not feasible. So you have to draw the line somewhere. Try this regex:

/^\s*[\w\-\+_]+(\.[\w\-\+_]+)*\@[\w\-\+_]+\.[\w\-\+_]+(\.[\w\-\+_]+)*\s*$/