SetTimeout Does not work for validation in jQuery -

below code: have written function form validation , works well. want call validation function after few seconds because feels more comfortable warn users few seconds after type field , it's less shocking. problem when paste "//this code" "//here" doesn't work , "settimeout called" doesn't show in console, , console triggers "if()" line in settimeout scope. guess problem scope of $(this) inner function don't know how solve it! :)

var firstname = $('#firstname'); var reg_firstname = /^[a-za-z]{1,50}$/;     var color_valid = "#e0ffe0"; var color_invalid = "#e09898"; var unable_btn = false; function validform (variable, reg_variable) {     variable.on('keyup',function(){         settimeout(function(){             // here:              console.log("settimeout called"); // called         },5000);         //this code:          if (reg_variable.test($(this).val()) == false || $(this).val().trim().length == 0) {             $(this).css("background-color", color_invalid);             unable_btn = false;             console.log("reg: " + reg_variable.test($(this).val()));             console.log("length: "+ $(this).val().trim().length);             console.log("btn: " + unable_btn);             console.log("===========");          } else {             $(this).css("background-color", color_valid);             unable_btn = true;             console.log("reg: " + reg_variable.test($(this).val()));             console.log("length: "+ $(this).val().trim().length);             console.log("btn: " + unable_btn);             console.log("===========");         }     }); } validform(firstname,reg_firstname);