I'm working on this calculator for JavaScript where a ice hockey goalie will be able to enter information to calculate his goals against average, or his GAA. I've got the calculator working (although I wish I could format the output to #.##, but oh well), but I want to be able to handle exceptions arising from say, a user entering a letter instead of a number, which would result in a NaN output via a try/catch statement, except I'm not sure how you would format it to look for NaN values. Any idea how I might go about doing that? Here is my code:
<!DOCTYPE html>
<html>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="http://www.w3schools.com/lib/w3.css">
<Title>Goals Against Average Calculator</Title>
<body>
<script src="modernizr.custom.05819.js"></script><!--Links to file containing modernizer library-->
<!-- Navigation -->
<nav>
<ul class="w3-navbar w3-black">
<li>Home</li> <!--Link to Home Page-->
<li>NHL Teams</li><!--Link to Page of NHL Teams-->
<li>AHL Teams</li><!--Link to Page of AHL Teams-->
<li>WHL Teams</li><!--Link to Page of WHL Teams-->
<li>G.A.A. Calculator</li><!--Link to GAA Calculator-->
<li>Fan Survey</li><!--Link to Fan Survey Page-->
</ul>
</nav>
<header>
<h1 style="text-align:center;">Goals Against Average Calculator</h1><!--Title of Page-->
</header>
<article>
<form>
<fieldset>
<label for="GoalsAllowed">
Enter Number of Goals Allowed
</label>
<input type="Goals" id="GoalsAllowed" /><!--Input for Goals Allowed-->
</fieldset>
<fieldset>
<label for="MinutesPlayed">
Enter Minutes Played
</label>
<input type="MinPlayed" id="MPlayed" /><!--Input for Minutes Played-->
</fieldset>
<fieldset>
<label for="GameLength">
Regulation Game Length
</label>
<input type="Minutes" id="MinGame" /><!--Input for Length of Regulation Game-->
</fieldset>
<fieldset>
<button type="button" id="button">Calculate</button><!--Calculation Button-->
</fieldset>
<fieldset>
<p id="GAA"> </p>
</fieldset>
</form>
</article>
<script>
function convert()
{
var Goals = document.getElementById("GoalsAllowed").value;
var Minutes = document.getElementById("MPlayed").value;
var GameLength = document.getElementById("MinGame").value;
var GAA = (Goals * GameLength) / Minutes;
//window.alert("Swords and Sandals: " + GAA);
document.getElementById("GAA").innerHTML = "Your Goals Against Average is: " + GAA;
}
document.getElementById("button").
addEventListener("click", convert, false);
</script>
</body>
</html>
EDIT: The comment about decimal formatting isn't why I'm posting. It was merely for cosmetic reasons on my part on what I would like it to look like, but it works fine as it is.
Others have provided answers about Number.isNaN, so I won't go into details on that; it's the right answer. :-)
As for your secondary question, how to format the number to two decimal places, all numbers have a function toFixed(numberOfPlaces) that returns a formatted string. Now, this function does not perform any rounding; it just chops off the remaining decimals. So for instance:
var num = 1.005;
var formatted = num.toFixed(2);
..will return "1.00". You probably want to round the input so that it gets handled and formatted consistently. To do that, there is a function Math.round() that you can call. It always rounds the number to have no decimals at all. You want two decimals, so that's a non-starter, right? Well, here's a little trick: If you multiply the number by 100 first, then you bump those two digits you want to keep to the left of the decimal. After rounding it, divide it by 100 to put them back in the right place.
Putting it all together:
var input = Number(prompt("Give me a number"));
if (Number.isNaN(input))
alert("That isn't a valid number!");
else
{
input = Math.round(input * 100) / 100;
var formatted = input.toFixed(2);
alert("Your input was: " + formatted);
}
You can also restrict the user to enter only number by using the type="number" to the input type in the HTML directly. HTML 5 introduces the number` type.
<input type="number" id="GoalsAllowed" /><!--Input for Goals Allowed-->
My experience is that the best way to check for NaN is a little verbose, but as far as I've seen it's bulletproof.
var numStr = prompt('Give me a number');
var num = Number.isNaN(Number(numStr));
If numStr was a valid number string, num will be false; if it was not, num will be true.
Why not just use Number.isNaN without converting to a number first? Well, Number.isNaN doesn't check whether a value is a Number or not, it literally just checks if it's NaN, so Number.isNaN('totally not a number') will return false.
Here is a JS Fiddle showing you what you can do: https://jsfiddle.net/iamjpg/huk8yp0L/
var convert = function() {
var Goals = document.getElementById("GoalsAllowed").value;
var Minutes = document.getElementById("MPlayed").value;
var GameLength = document.getElementById("MinGame").value;
var regex = /^[+-]?\d+(\.\d+)?$/
if (!regex.test(Goals) || !regex.test(Minutes) || !regex.test(GameLength)) {
alert('Please only enter numeric values.');
return false;
}
var GAA = (Goals * GameLength) / Minutes;
//window.alert("Swords and Sandals: " + GAA);
document.getElementById("GAA").innerHTML = "Your Goals Against Average is: " + Math.ceil(GAA * 100) / 100;
}
document.getElementById("button").addEventListener("click", convert, false);
var regex = /^[+-]?\d+(\.\d+)?$/ - Checks if you are entering a number or float.
Math.ceil(GAA * 100) / 100; - Rounds your calculated value to the nearest hundredth.
Hope this is helpful.
You have to convert each value to number
goal = +goal
and check if it is a number
if(isNaN(goal)){
// show error
}else{
// show result
}
Related
I'm trying to calculate the number of payments but output was wrong so i tried to calculate a simple operation on the month value.But "+" operator doesn't sum my values it acts like string.For example 3 and 5,output isnt 8 its 35.
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Mortgage Calculator</title>
<script>
function validateForm() {
var principal = princ.value;
var interestrate = interest.value;
var monthlypayment = monthly.value;
var months=(principal)+(interestrate);
document.getElementById("demo").innerHTML=months;
}
</script>
</head>
<body>
<p id="demo"></p>
<form name="myForm" action="/action_page.php" onsubmit="return validateForm()" method="post">
Principal: <input type="text" id="princ" name="principal">
<br>
<br> Interest Rate: <input type="text" id="interest" name="interestrate">
<br/>
<br/> Monthly Payment: <input type="text" id="monthly" name="monthlypayment">
</form>
<button onclick="validateForm()">Run</button>
</body>
</html>
The values you are summing are strings. You need to convert them to integers:
parseInt(principal)+parseInt(interestate)
The reason for this is that input values are always strings. AFAIK, this is even if you set the type to number. parseInt(s) converts a string s to an int.
The actual type of the value is string. That's why string concatenation is happening. You have to use parseInt to convert string to integer to perform intended arithmetic operation.
Change:
var months=(principal)+(interestrate);
To:
var months = parseInt(principal) + parseInt(interestrate);
var months=parseInt(principal)+parseInt(interestrate);
Values need to be converted to an integer first.
Your input values are treated as string as they are textbox inputs. Parse the values first before adding them up.
e.g.
var principal = parseInt(princ.value);
var interestrate = parseInt(interest.value);
I apologize for the basic question but I have been trying to make this work for a long time and I just can't seem to get this code to return a value.
I am embarrassed to admit how long I have been attempting to make it work, and how many StackOverflow questions that were related that I have looked at, however, none were as simple as my code, and when I attempted to make something closer to how mine looked, it just wouldn't alert anything.
The idea is the following:
User inputs 2 numbers,
clicks the button,
and is alerted the average of the numbers they input.
My alert has been NaN no matter how many iterations I have made. I could really use some advice. Thanks in advance!
<html>
<head>
<title> Javascript </title>
<body>
<p> Enter two number for an average below </p>
<p> Number 1<input type="text" id="userInput1"></input></p>
<p> Number 2<input type="text" id="userInput2"></input></p>
<button id="averageButton"> Calculate</button>
<script type="text/javascript">
function average(a, b) {
return ((a + b) /2);
}
document.getElementById("averageButton").onclick = function (){
var a = document.getElementById("userInput1").value;
var b = document.getElementById("userInput2").value;
alert(average());
}
</script>
</body>
</html>
You failed to pass the numbers a,b to your function - a simple mistake.
But since the inputs are seen as strings you also need to convert them to numbers a*1
See commented code
<html>
<head>
<title> Javascript </title>
<body>
<p> Enter two number for an average below </p>
<p> Number 1<input type="text" id="userInput1"></input></p>
<p> Number 2<input type="text" id="userInput2"></input></p>
<button id="averageButton"> Calculate</button>
<script type="text/javascript">
function average(a, b) {
// force the input as numbers *1
return ((a*1 + b*1) /2);
}
document.getElementById("averageButton").onclick = function (){
var a = document.getElementById("userInput1").value;
var b = document.getElementById("userInput2").value;
// pass the numbers to the average function!
alert(average(a,b));
}
</script>
</body>
</html>
At first glance you might need to convert your input values from strings to floats and actually pass them to the average function.
You may want to change the inputs to
<input type="number"> to prevent users from adding non-numeric values.
Secondly parse your inputs as document....value returns string,
var a = parseFloat(document.getElementById("userInput1").value);
var b = parseFloat(document.getElementById("userInput2").value);
If you do just this you wouldn't have to deal into the funny business of doing a*1.
// force the input as numbers *1
return ((a*1 + b*1) /2);
This block isn't required since multiplying a string with a number returns a NaN value.
function average(a, b) {
return ((a + b) / 2);
}
document.getElementById("averageButton").onclick = function() {
var a = document.getElementById("userInput1").value;
var b = document.getElementById("userInput2").value;
alert(average());
}
<p> Enter two number for an average below </p>
<p> Number 1<input type="text" id="userInput1"></input>
</p>
<p> Number 2<input type="text" id="userInput2"></input>
</p>
<button id="averageButton"> Calculate</button>
I am trying to create a simple "guess the number game" in a web page where a user is the one thinking of the number and the computer is to guess the number that the user is thinking (no user input required). I need to create three buttons for user to respond to the computer's guess: Guess Higher, Guess Lower, Correct. I am not sure how to make the GuessHigher() and GuessLower() function work. Here is the java script code:
function getFieldValue(target) {
var elm = document.getElementById(target);
var val = parseInt(elm.value);
return val;
}
function getCompGuess() {
var upper = getFieldValue("UPPER");
var lower = getFieldValue("LOWER");
return (parseInt((upper + lower) / 2))
}
/* User starts game. */
function play() {
var remaining = getFieldValue("REMAINING");
var compGuess = getCompGuess()
var compElm = document.getElementById("COMP_GUESS")
compElm.innerHTML = compGuess
}
function GuessHigher() {
}
function GuessLower() {
}
function correct() {
alert ("YAY! Thank you for playing");
}
Here is the HTML code:
<html>
<head>
<meta charset="UTF-8">
<script src="lab1a.js"></script>
</head>
<body>
Guess a number game: <br/> <br/>
Upper Bound: <input id="UPPER" type="text"></input> <br/>
Lower Bound: <input id="LOWER" type="text"></input> <br/>
Guesses Remaining: <input id="REMAINING" type="text"></input> <br/>
<button onclick="play()">Play!</button> <br/>
Computer's Guess: <span id="COMP_GUESS"></span> <br/>
<button onclick="GuessHigher()">Guess Higher</button>
<button onclick="GuessHigher()">Guess Lower</button>
<button onclick="correct()">Correct!!!</button>
</body>
</html>
GUESS HIGHER:
It might not be elegant, but you could try to take the number last guessed and ADD to it any number within difference of UPPER BOUND-LAST GUESS. For example, lets say we have a number line with UPPER=10 and LOWER=0
0|----------|10
and we guess 5 as the computer. Now, if we want to guess higher we're going to need a place holder for our OLD Guess (5), and were going to need to decrease the guessing range so we don't go over our Upper boundry.
0|----<5>----|10, Imagine zooming in on only the top half 5>---10:
5>----|10.
This new range I called availableGuessingRange which is equal to 10-5 or 5.
We're only going to let the computer pick a new number between 1 and 5 now using Math.random.
Let's say it picks 3. Now we can bring that number back to our old guess by adding it (ie. 5+3=8), now 8 is the computers NEW GUESS.
I think it could be something like this:
var lastGuess=document.getElementById("COMP_GUESS").value
var avaliableGuessingRange = upper-lastGuess;
return Math.floor(Math.random()*avaliableGuessingRange)+lastGuess
for GUESS LOWER: I think it would be a similar set up except it uses lastGuess-lower to create the new range and you'll be subtracting the new guess from the last guess to move DOWN the number line.
The way I've written the code currently won't work because of variable scopes, but I think the logic should work.
I made fiddle out of this, and refactor the code tini little bit, inline listeners are considered bad practice. You should consider using some linter as there was some syntax error, mainly you were not terminating your statements; <--- See, this was typo actually, I terminated the sentence accidently with ; instead of .
(function() {
//getting references to buttons
var high = document.getElementById('high');
var lower = document.getElementById('lower');
var btn_correct = document.getElementById('correct');
//setting listeners
high.addEventListener('click', GuessHigher);
lower.addEventListener('click', GuessLower);
btn_correct.addEventListener("click", correct);
function getFieldValue(target) {
var elm = document.getElementById(target);
return parseInt(elm.value);
}
function getCompGuess() {
var upper = getFieldValue("UPPER");
var lower = getFieldValue("LOWER");
return (parseInt((upper + lower) / 2));
}
/* User starts game. */
function play() {
var remaining = getFieldValue("REMAINING");
var compGuess = getCompGuess();
var compElm = document.getElementById("COMP_GUESS");
compElm.innerHTML = compGuess;
}
function GuessHigher() {
console.log('higher');
}
function GuessLower() {
console.log('lower');
}
function correct() {
console.log("YAY! Thank you for playing");
}
}());
<body>
Guess a number game:
<br/>
<br/>Upper Bound:
<input id="UPPER" type="text">
<br/>Lower Bound:
<input id="LOWER" type="text">
<br/>Guesses Remaining:
<input id="REMAINING" type="text">
<br/>
<button id='play'>Play!</button>
<br/>Computer's Guess: <span id="COMP_GUESS"></span>
<br/>
<button id='high'>Guess Higher</button>
<button id='lower'>Guess Lower</button>
<button id='correct'>Correct!!!</button>
</body>
Try using code below
Math.floor(Math.random()*1000) // return a number between 0 and 1000
to generate random numbers
And use if else statements for
High, low , correct
I am trying to write a short piece of html code that, given two initial amounts, attempts to find the number greater than or equal to the first that wholly divides the second given amount. The code tries to divide the numbers, and if it is unsuccessful, adds 1 to the first number and tries to divide again, etc...
I want the code to return the value that does wholly divide the second number AND the answer to the division (with some plain text appearing around it).
Added to this, or at least I'd like there to be, is that upon clicking one of 5 different buttons a multiplication operation is performed on the first given number, it is rounded up to the nearest whole number, and THEN the function attempts to divide this into the second given number.
It's difficult to explain exactly what I want without showing you the code I have so far, so here it is:
<html>
<head>
<b>Rounded Commodity Pricing:</b><br>
<script language="Javascript">
function finddivid(marketprice,tradevalue) {
var KWDex = 0.281955
var GBPex = 0.625907
var USDex = 1
var CADex = 0.998727
var EURex = 0.784594
if
(currency == "KWD")
var currencyMarketprice = Math.ceil(marketprice*KWDex)
else if
(currency == "GBP")
var currencyMarketprice = Math.ceil(marketprice*GBPex)
else if
(currency == "USD")
var currencyMarketprice = Math.ceil(marketprice*USDex)
else if
(currency == "CAD")
var currencyMarketprice = Math.ceil(marketprice*CADex)
else if
(currency == "EUR")
var currencyMarketprice = Math.ceil(marketprice*EURex)
if (tradevalue % currencyMarketprice == 0)
return ("tonnage = " + tradevalue / currencyMarketprice + " mt, and price = " + currencyMarketprice +" " +currency +" per mt");
else
{for (var counter = currencyMarketprice+1; counter<(currencyMarketprice*2); counter++) {
if (tradevalue % counter == 0)
return ("tonnage = " + tradevalue / counter + " mt, and price = " + counter +" " +currency +" per mt");}}};
</script>
</head>
<p>Select currency:
<input type="button" value="KWD" OnClick="var currency = KWD">
<input type="button" value="USD" OnClick="var currency = USD">
<input type="button" value="GBP" OnClick="var currency = GBP">
<input type="button" value="EUR" OnClick="var currency = EUR">
<input type="button" value="CAD" OnClick="var currency = CAD">
<P>Enter today's price of commodity in USD: <input name="mktprc" input type="number"><br><p>
<P>Enter value of trade: <input name="trdval" input type="number">
<input type="button" value="Calculate" OnClick="showMeArea.value=finddivid(mktprc,trdval);">
<p>
<br><br>
<input name="showMeArea" readonly="true" size="30">
</html>
If you run this html in your browser you should see what I am trying to achieve.
It is far from complete but here are the main problems/features that I need help with:
I would like to be able to click on one of the 'currency' buttons so that upon clicking, the variable 'currency' is assigned and then used in the function finddivid.
(2. This isn't as important right now, but eventually, once this is working, I'd like it so that upon clicking one of the currency buttons, it changes colour, or is highlighted or something so that the user knows which currency rate they are using.)
Upon entering the numbers into the two boxes I would like to click 'Calculate' and have it return what I've written in the function into the 'showMeArea' read-only box at the end of the code.
I know I'm probably missing loads of stuff and I might be miles away from success but I am very new to programming (started 4 days ago!) so would like any like of help that can be offered.
Thanks in advance of your comments.
The first request requires that you put the currency into the actual script, and I would recommend using a setter function:
<script language="Javascript">
var currency; // you might want to set this at a default just in case
function setCurrency(val) { currency = val; } // Setter function
function finddivid(marketprice,tradevalue) {
Then call it in your button click:
<input type="button" value="KWD" onClick="setCurrency('KWD');">
As for the second request, I'd say you have the concept down well enough, but you don't have the method exactly right. First your inputs will need an id attribute:
<input name="mktprc" id="mktprc" input type="number">
<input name="trdval" id="trdval" input type="number">
The name attribute is used for posting values, the id attribute is used by javascript to find elements within a page. Using jQuery would make retrieving these elements easy, but I'll show both the jQuery and the standard JavaScript method of doing this:
jQuery:
<input type="button" value="Calculate" OnClick="$('#showMeArea').val(finddivid($('#mktprc'),$(#'trdval')));">
The $('#id') selects an element. The method .val() sets the value.
Note for the jQuery purists: Yes, there are much better/sophisticated ways to accomplish this with jQuery, but this answer is targeted to my perception of OP's JavaScript capability.
Standard Javascript:
<input type="button" value="Calculate" OnClick="document.getElementById('showMeArea').value = finddivid(document.getElementById('mktprc'),document.getElementById('trdval'));">
i have a small javascript form
<div id="calculator-text"><h2>Tape calculator - based on cable size 1 mm to 28 mm, with 15% overlap</h2></div>
<form name="form1" method="post" action="">
<div id="calcformlabel"><label for="val2">Enter your cable size</label> (in mm)</div>
<div id="calcformtext1"><input type="text" name="val2" id="val2"></div>
<div id="calcformbutton"><input type="button" name="calculate" id="calculate" value="Calculate"></div>
<div id="calcformresult">The tape size you require is:- <span id="result1" class="maintext1"></span> (mm)</div>
</form>
<script type="text/javascript">
var btn = document.getElementById('calculate');
btn.onclick = function() {
// get the input values
var val2 = parseInt(document.getElementById('val2').value);
// get the elements to hold the results
var result1 = document.getElementById('result1');
// create an empty array to hold error messages
var msg = [];
// check each input value, and add an error message
// to the array if it's not a number
if (isNaN(val2)) {
msg.push('<span class="maintext1">Enter your cable size</span>');
}
// if the array contains any values, display the error message(s)
// as a comma-separated string in the first <span> element
if (msg.length > 0) {
result1.innerHTML = msg.join(', ');
} else {
// otherwise display the results in the <span> elements
result1.innerHTML = val2 * 3.142 * 1.15;
}
};
</script>
basically this is a simple calculation
a) how can i get this to output to 2 decimal places (and obviously round up or down depending on -.5 = round down and +.5 = round up)
b) replace the input type button for an image ( i have tried the obvious code and >input type = image>, basically these do actually work but instead of displaying the actual result, they display the result in a split second then reload the page with the blank form again...
any help on this would be much appreaciated
thanks in advance
for a part of your question
you can round javascript to specific precision by
Link :Number rounding in JavaScript
var original=28.453
1) //round "original" to two decimals
var result=Math.round(original*100)/100 //returns 28.45
2) // round "original" to 1 decimal
var result=Math.round(original*10)/10 //returns 28.5
3) //round 8.111111 to 3 decimals
var result=Math.round(8.111111*1000)/1000 //returns 8.111
The .toFixed() method lets you round off to n decimal places, so:
result1.innerHTML = (val2 * 3.142 * 1.15).toFixed(2);
I think the problem you're having with the image is that <input type="image"> defines the image as a submit button. Perhaps just include a standard image with an <img> tag rather than <input type="image">. If you give it an id='calculate' it should still work with your existing JS.
Or you could use a button element containing an img element so that you can specify the type (as not being submit):
<button type="button" id="calculate"><img src="yourimage"></button>
(I'm not sure that you need a form at all for this functionality since you don't seem to want to submit anything back to the server.)
To swap the button for an image, replace the button <input> with this code:
<img src="http://www.raiseakitten.com/wp-content/uploads/2012/03/kitten.jpg" name="calculate" id="calculate" value="Calculate" onclick="document.forms['form1'].submit();" />
It adds the image and a submit function for your form.
To round to two decimal places, use this function:
function twoDP(x){
return Math.round(x*100)/100
}
use it like this:
twoDP(100/3) //returns 33.33
it might also be relevant for you to use Math.PI
var result = val2 * Math.PI * 1.15 ;