Common example: JS formatted mobile phone number 3 4 4 form

How to convert the format to 3 4 4 when filling in the phone number:

A: When filling the mobile phone number, in the KeyUp event to determine the length, when eligible to insert a space after the value

$ (' #username '). On (' KeyUp ', function (e) {var val  = $ (this). Val ();//The key is deleted to perform the following judgment, otherwise deleted to the third and eighth bit when the space, has been circulating. if (E.keycode = = = 8) {$ (this). Val (val); return;} if (val.length = = = 3 | | val.length = = 8) {val + = "; $ (this). Val (val)})

Second: The regular expression validation when you want to remove the space

var phone = $ (' #username '). Val (). replace (/\s/g, ");

　　

Common example: JS formatted mobile phone number 3 4 4 form