I was recently working on an assignment for my computer class, but I have a connection error within my code. To my knowledge, the function looks correct.

            function idCard(){
            var firstName = document.getElementByID("firstName").value;
            var lastName = document.getElementByID("lastName").value;
            var address = document.getElementByID("address").value;
            
            document.getElementById("postFullName").innerHTML = firstName + "" + lastName;
            document.getElementById("postAddress").innerHTML = address;
            
            var age = document.getElementByID("age").value;
            var phoneNumber = document.getElementByID("phoneNumber").value;
            
            const numberArray = [age,phoneNumber];
            
            for ( var i = 0; i < numberArray.length; i++){
                if (numberArray[i]<=100){
                document.getElementId("postAge").innerHTML = numberArray[i];
                }
                else{
                document.getElementId("postPhoneNumber").innerHTML = numberArray[i];
                }
            }
            
            }

The display works fine, and so far I only get one error from my debugging console,"Uncaught TypeError: document.getElementByID is not a function".