不知道如何编码这个jQuery

Question

This is kinda hard to explain. Ok so i have this text input ("textmoney') that you enter a number into it and it will give the estimated amount of money made a year. So when a person types in their number and hits enter they can see their answer. Lets say that they want to enter another number so they backspace all the numbers in the text input until nothing is there. Basically i want to have it so when the numbers are no longer in the text input box the answer to their first number disappears. Im sorry if you don't understand what I'm trying to say because i really don't know how to explain this. (ex: When you type something into google and decide to type in something else you delete what you typed in and the search results disappear.)

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
    <script>
    $('#textmoney').keydown(function (e){
    if(event.keyCode == 13){
        moneyFunction();
    }})

    $(document).keydown(function (e) {
        if(event.keyCode == 82) {
            reloadFunction();
    }})

    $(document).ready(function() {
        $('#textmoney').keydown(function() {
            $('#redotext').css('visibility', 'visible');
    })})

    $('#textmoney').mouseover(function() {
        $('#textmoney').css('border', '1px solid black');
    $('#textmoney').mouseout(function() {
        $('#textmoney').css('border', '1px solid grey');
    })})
    </script>

    <script>
    function moneyFunction() {
        var money = document.getElementById('textmoney').value;
        var dailyE = money/365;

        document.getElementById('demo').innerHTML = ("$" + dailyE + " " + "per day");


    if ( document.getElementById('textmoney').value == 0) {
        document.getElementById('demo').innerHTML = "You aint enter no chang";
    }
    }   //Function tag

    function reloadFunction() {
        location.reload();
    }
    </script>

Answer 1

Here's how I would reorder this a bit to meet your requirements and make it a little easier to read.

$(document).ready(function() {

    var $demo = $('#demo');
    var $textMoney = $('#textmoney')
    .keyup(function(e) {
        if (e.keyCode === 13) {
            var money = $(this).val();
            if (isNaN(money) || money === '') {
                $demo.text('You ainy enter no chang');
            } else {
                var dailyE = $(this).val() / 365;
                $demo.text('$' + dailyE + ' per day');
            }
        } else if ($(this).val() === '') {
            $demo.text('');
        }
    }).mouseover(function() {
        $(this).css('border', '1px solid black');
    }).mouseout(function() {
        $(this).css('border', '1px solid grey');
    });

});

JSFiddle: https://jsfiddle.net/ws6cosh4/1/

Answer 2

I think I know what you mean. Is it something like this?

http://jsfiddle.net/m8oef0ju/

$("#textmoney").on('input',function () {
    $("#answer").hide();
});

Answer 3

Simple on textbox input event chaeck whether it's empty or not. If it's empty then remove data.

$("#textbox").on('input',function() {
    if(("#textbox").val().length() == 0){
      //your code goes here.
    }
});

Answer 4

var textbox = document.getElementById("textbox")

textbox.addEventListener('input', function(event) {
    event.preventDefault();

    if (!!textbox.length) {
        //enter code here
    }
})