Focus event occurs when an element (such as links or form) gain or lose focus.
Example:
. 1 <! DOCTYPE HTML> 2 <HTML lang = " EN " > . 3 <head> . 4 <Meta charset = " UTF-. 8 " > . 5 <title> Focus Events </ title> . 6 </ head> . 7 <body> . 8 <h1> lost focus after transfer capital </ h1> 9 <the p-> input character can be converted to uppercase! </ the p-> 10 <the INPUT the above mentioned id = " S " > 11 <br> <br> 12 <the Button> Click me, input loses focus </ the Button> 13 <the p-the above mentioned id = " var the EL = document.getElementById ( ' S ' ); 16 EL.addEventListener ( ' Blur ' , CheckKey, to false ); . 17 18 is function CheckKey (E) { . 19 var STR = EL.value; 20 is Alert ( " character you typed They are: " + STR); 21 is OUT .textContent = str.toUpperCase (); 22 is } 23 is </ Script> 24 </ body> 25 </ HTML>