JSFiddle - React, Tailwind, and code Playground

HTML

Identity number : <input type="text" name="id_number" maxlength="13"><br>
Birthdate: <input type="text" class="datepicker" name="birthdate"><br>
Gender: <input type="text" name="gender"><br>

JavaScript

var $input1 = $("input[name=id_number]"),
    $input2 = $("input[name=birthdate]"),
    $input3 = $("input[name=gender]");

$input1.on("keyup", function(){
		
	var id = $input1.val().split(" "), // gets the ID number you typed
        birthdate="",
        gender="",
        part1 = id[0],
        part2 = id[1];
    
    console.log($input1.val());
    
    if(part1.length>5) birthdate = part1.substr(0,2) + "/" + part1.substr(2,2) + "/" + part1.substr(4,2);
	
	$input2.val(birthdate);
    
    if(part2 && part2.length){
         if(parseInt(part2[0]) <5)
             gender = "Female"
         else
             gender = "Male"
      
        $input3.val(gender);
    }
	
})