Server and client email address verification function

There are many ways to verify email address. On the browser side, js mailbox validation can be detected by regular expressions.
Code is as follows

function isEmail(email) { return /^((([a-z]| d| [!#$%&'*+-/=?^_`{| }~]| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])+(.([a-z]| d| [!#$%&'*+-/=?^_`{| }~]| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])+)*)| ((x22)((((x20| X09)*(x0dx0a))?(x20| X09)+)?(([x01-x08x0bx0cx0e-x1fx7f]| X21| [x23-x5b]| [x5d-x7e]| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])| (\\([x01-x09x0bx0cx0d-x7f]| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF]))))*(((x20| X09)*(x0dx0a))?(x20| X09)+)?(x22)))@((([a-z]| d| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])| (([a-z]| d| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])([a-z]| d| -| .| _| ~| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])*([a-z]| d| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF]))).)(([a-z]| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])| (([a-z]| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])([a-z]| d| -| .| _| ~| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])*([a-z]| [u00A0-uD7FFuF900-uFDCFuFDF0-uFFEF])))$/i.test(email); }

or

function validateEmail(elementValue) { var emailPattern = /^[a-zA -Z0-9._]+[a-zA-Z0-9]+@[a-zA-Z0-9]+.[a-zA-Z]{2,4}$/; return emailPattern.test( elementValue); }

function checkEmail(mail) { return /^[w-]+(.[w-]+)*@([a-z0-9-]+(.[a-z0 -9-]+)*?.[az]{2,6}| (d{1,3}.){3}d{1,3})(:d{4})?$/.test(mail); }

The call is simple:
Code

if (isEmail('[email protected]')){ console.log(' www.45it.net This is email is valid'); }View Code

If it is server side verification. Like php, the simplest one is:
The code is as follows

$a='/([w._]{2,10})@(w{1,}).([az]{2 ,4})/'; $b='[email protected]';

if(preg_match($a,$b)){ echo "email legal"; }else{ echo " E-mail is not legal. "; }

You need to assert whether a string of strings matches. Such as ^ $ /^([w._]{2,10})@(w{1,}).([a-z]{2,4})$/Note that the header and the tail are added ^ $