if (form.text1.value == "") alert("Please Enter a String"); else alert("Hi! "+form.text1.value+"Welcome to JavaScript"); }
<input type=text name="email" value="" onBlur="emailcheck(this.form)"> This code calls the function emailcheck
function emailcheck(form) { if (form.email.value == "" || form.email.value.indexOf('@', 0) == -1) alert("No valid e-mail address!"); else alert("OK!"); }