I have some code here that will make validations of whether or not the input from a text box is NOT an empty string and isNaN. When i do these validations on amounts entered, i would like it to add them up.. however when a user does not enter anything in one or more amount fields the program should just add entered fields. But instead i get NaN showing in the total field.
link to full code: http://jsfiddle.net/KxNqQ/
var $ = function (id) {
return document.getElementById(id);
}
var calculateBills = function () {
var myErrorFlag = "N";
for (i = 1; i <= 4; i++) {
AmountNumber = 'amount' + i;
AmountValue = $(AmountNumber).value;
if (AmountValue != "" && isNaN(AmountValue)) {
$(AmountNumber).style.color = "red";
myErrorFlag = "Y";
} else {
$(AmountNumber).style.color = "black";
myErrorFlag = "N";
}
}
if (myErrorFlag != "Y") {
var Amount = 0;
for (i = 1; i <= 4; i++) {
Amount += parseInt($('amount' + i).value,10);
}
$('total').value = Amount;
}
}
var clearFields = function () {
for (i = 1; i <= 4; i++) {
itemName = 'item' + i;
$(itemName).value = "";
}
for (i = 1; i <= 4; i++) {
amountName = 'amount' + i;
$(amountName).value = "";
}
$('total').value = "";
}
window.onload = function () {
$("clearfields").onclick = clearFields;
$("addbills").onclick = calculateBills;
}
I think you've got your requirements a little bit confused, or at the very least I was confused by them. So in order to answer your question, I'm going to rephrase the requirements so I understand them better. This is a useful exercise that I try to do when I'm not 100% sure of the requirements; if I can't get the requirements right, what's to say I'll get the code right?
So the requirements – as I understand them – are:
Given each amount input
When the input has a value
And that value is a number
Then add the value to the total
And make the input color black
But if the input does not have a value
Or that value is not a number
Then make the input color red
Going through your code, I can see a number of problems with it. First, I noticed that both AmountNumber and AmountValue are global variables, because they were not declared local with the var keyword. So before fixing our code, let's change that. Let's also change the variable names to something that more accurately describe what they are, hopefully making the code easier to understand:
var input = $('amount' + i);
var value = input.value;
Now, note that I chose to store the element in the input variable. This is so we don't have to look it up multiple times within the loop. Looking things up in the DOM can be expensive so we'll want to keep it to a minimum. There are other was to look up elements as well, such as getElementsByClassName, querySelector and querySelectorAll; those are left as an exercise for the reader to research and evaluate.
Next, in each iteration of the loop, you check that AmountValue is not a string and simultaneously is not a number:
if (AmountValue != "" && isNaN(AmountValue)) {
This will be true so long as AmountValue is truthy (which is the case for non-empty strings) and so long as isNaN thinks it's a number (which is the case for strings that contain numbers.) It really is rather confusing; if I understand your code correctly this clause is there to check for invalid input and if it is true should mark the input field red and set a flag. I.e. this is the but clause in the aforementioned requirements.
Let's rewrite this to be the when clause instead, we'll take care of the but later. Before we do that, let's look at the myErrorFlag. It's used – I think – to see whether all input is well formed and in that case, add it all up. Well, validation and summation can be done in one fell swoop, so let's get rid of the flag and sum the values while validating them. So we replace myErrorFlag with a total variable:
var total = 0;
Now, let's get back to our clause. The requirements say:
When the input has a value
And that value is a number
Then add the value to the total
In code, that should look something like this:
if (value && !isNaN(value)) {
total += parseInt(value, 10);
input.style.color = 'black';
}
There are a couple of things going on here. For one, the if statement has been turned on its head a bit from what it was. It first checks to see that value is truthy, then that it is a number. The second check can be a bit tricky to read, because it is essentially a double negation; in english it reads "is not not a number", i.e. "is a number". I'll leave it as an exercise for the reader to figure out whether there's a more easily understood way of writing this check.
Now what about the but clause in our requirements?
But if the input does not have a value
Or that value is not a number
Then make the input color red
Well, it's essentially the inverse of our previous statement, so let's simply add an else clause:
else {
input.style.color = 'red';
}
Because the requirements doesn't mention the total variable in this clause, it is simply ignored and doesn't show up in the end result.
Adding it all up (no pun intended) the code – with comments – looks like this:
var calculateBills = function () {
var total = 0;
for (i = 1; i <= 4; i++) {
// Given each amount input
var input = $('amount' + i);
var value = input.value;
if (value && !isNaN(value)) {
// When the input has a value
// And that value is a number
// Then add the value to the total
total += parseInt(value, 10);
// And make the input color black
input.style.color = 'black';
} else {
// But if the input does not have a value
// Or that value is not a number
// Then make the input color red
input.style.color = 'red';
}
}
$('total').value = total;
};
There are more things that could be learned from this to make for better code. For instance, this code will break if the number of inputs change, or if their id names change. This is because they are selected specifically by their IDs and as such, if those change then this code will no longer function.
Another potential issue is that we're setting inline styles on the inputs as we loop over them. This means that in order to keep this code up to date with the styling of the site, it'll have to change. Generally, mixing styling and functionality like this is not a good idea and should be avoided. One way of doing so is to use class names instead, and toggle these on and off. Incidentally, this could also help the previous problem I mentioned.
There are other problems as well, but we'll leave those for another day. Hope this helps!
Try this
var calculateBills = function () {
var Amount = 0;
for (i = 1; i <= 4; i++) {
var AmountElement = $('amount' + i),
AmountValue = AmountElement.value;
if (AmountValue != "" && !isNaN(AmountValue)) {
AmountElement.style.color = "red";
Amount += parseInt(AmountValue,10);
} else {
AmountElement.style.color = "";
}
}
$('total').value = Amount;
};
Demo
Anyway, instead of using elements with id like id="amount1", id="amount2", id="amount3", etc., you could use classes (e.g class="amount") and get them with .getElementsByClassName
Related
I am making a memory game using Javascript, HTML, and CSS.
Here is a brief description of the game:
The program generates a random number, which is shown on
screen.
After about 5 seconds, the number disappears and a pop-up box appears on the screen, asking for the user to enter the number he or she just saw.
If the number matches the one that was previously on screen, then an alert box with the word "Correct" appears. If not, an alert box with the text "Nope. Nice try" appears.
Here's my problem:
The alert box says "Nope. Nice try" even when I enter the correct number.
Here is what I've coded thus far:
(Keep in mind that I have yet to any implement setInterval/setTimeout functions. I made the "hide" function manual for convenience.)
JS:
/* game level = easy
numbers from 1-9000 are generated */
function random(a){
a = Math.floor(Math.random() * (9000 - 1) + 1);
document.getElementById("screen").innerText = a;
}
function getInput(a){
var input = window.prompt("Enter the number you just saw:");
if(input === a){
alert("Correct!");
}
else{
alert("Nope. Nice try.");
}
}
/* hide toggle */
function hide() {
var x = document.getElementById("screen");
if (x.style.display === "none") {
x.style.display = "none";
} else {
x.style.display = "none";
}
}
My question: Would it be ideal to use an array of numbers from 1-9000 instead?
With an array, I figure I can do something like this:
for(var i = 0; i < arr.length; i++){
if(//){
}
else{
}
}
Thank you for reading.
From what I can tell, you are treating a as a variable with a scope larger than it actually has. a is an argument, and its scope doesn't reach beyond the function it is declared in.
In this case, a in random(a) and a in getInput(a) are two unrelated entities with a scope that doesn't overlap.
A solution could be to make a a global variable and declare it outside of any function, like
var a;
function random(){
a = Math.floor(Math.random() * (9000 - 1) + 1);
document.getElementById("screen").innerText = a;
}
function getInput(){
var input = window.prompt("Enter the number you just saw:");
if(input == a){ // make '===' into '==' instead btw
alert("Correct!");
}
else{
alert("Nope. Nice try.");
}
}
I see that you receive a String from the user, but you try to compare it to an integer. So lets say that a = 1, and input ='1' , which means they will never be equal.
You should onvert the string to an int and after that do the comparison.
Try
input == a
Instead of
input === a
Math.random returns a number and you're comparing it against a string with type match.
console.log(1 === '1');
console.log(1 == '1');
EDIT I originally posted this with my version of the J.S but it's so far off no one can even help so i'm starting over. Here is the pseudocode i have done that needs to be translated into a Javascript program. Any help is appreciated!
I am a beginning programmer i understand this code will have multiple errors, that's why i am here. Array's and loops have given me much trouble while trying to learn them and especially with formatting them in JavaScript. The things i know are incorrect or still need i commented out i still need them, i also know i'm not passing anything i just can't seem to wrap my head around how to get them there. I'm also not sure if while gather input i'm using alter and prompt correctly. In the display function the spacing is necessary for when it will be displayed. Corrections and explanations are greatly appreciated.
Module main()
//Declare local variables
Declare endProgram = “no”
While endProgram == “no”
Declare Real notGreenCost[12]
Declare Real goneGreenCost[12]
Declare Real savings[12]
Declare String months[12] = “January”, “February”, “March”, “April”, “May”, “June”, “July”, “August”, “September”, “October”, “November”, “December”
//function calls
getNotGreen(notGreenCost, months)
getGoneGreen(goneGreenCost, months)
energySaved(notGreenCost, goneGreenCosts, savings)
displayInfo(notGreenCost, goneGreenCosts, savings, months)
Display “Do you want to end the program? Yes or no”
Input endProgram
End While
End Module
Module getNotGreen(Real notGreenCost[], String months[])
Set counter = 0
While counter < 12
Display “Enter NOT GREEN energy costs for”, months[counter]
Input notGreenCosts[counter]
Set counter = counter + 1
End While
End Module
Module getGoneGreen(Real goneGreenCost[], String months[])
Set counter = 0
While counter < 12
Display “Enter GONE GREEN energy costs for”, months[counter]
Input goneGreenCosts[counter]
Set counter = counter + 1
End While
End Module
Module energySaved(Real notGreenCost[], Real goneGreenCost[], Real savings[])
Set counter = 0
While counter < 12
Set savings[counter] = notGreenCost[counter] – goneGreenCost[counter]
Set counter = counter + 1
End While
End Module
Module displayInfo(Real notGreenCost[], Real goneGreenCost[], Real savings[], String months[])
Set counter = 0
While counter < 12
Display “Information for”, months[counter]
Display “Savings $”, savings[counter]
Display “Not Green Costs $”, notGreenCost[counter]
Display “Gone Green Costs $”, goneGreenCost[counter]
End While
End Module
A few notes:
Currently the program creates a few variables and functions that
don't seem to interact
Most of the edits below are not optimal - there are parts that
could be done by much simpler means (i.e. counter++) - But thats
for you to learn =P
I made quite a few assumptions of what you wanted the program to
do, they might be wrong, they might be right
var notGreenCost = []; //Array lengths don't need to be specified
var goneGreenCost = [];
var savings = [];
var months = ["January", "Feburary", "March", "April", "May", "June"];
//A boolean value (true | false) would suit this better as opposed to "yes"/ "no"
var endProgram = false;
var option = 0;
/* You dont need main functions in javascript
* migrated everything to be global :/
* Delete:
function main(){
// Move this (made it global): var endProgram = "no";
}
*/
// I don't think this is meant to be initMonths..
// Maybe something like getOptions?
function /*initMonths*/getOptions(){
while (endProgram == false){ //lowercase while
//Because prompt would block everything else until it gets input
//we probably want to move the prompt to be after the alerts
alert("options:"); //Clarity
alert("1 to enter data");
alert("2 to display data");
alert("3 to write data to a file");
alert("4 to read data from a file");
//Alter global "option" to take the value of the prompt
option = prompt("What would you like to do? Type:");
//} //I assume you want the rest of the code in this while loop - otherwise it will loop forever
// Delete this bracket (its unmatched): {
// Delete return statement as it will stop the function return option;
// Delete this bracket (its unmatched): }
//Create a variable to take the value of prompt (this should be outside the while loop) but it seem clearer for explanation purposes to be here
var toEnd;
toEnd = prompt("Do you want to end the program (enter yes or no)");
// Javascript uses != for "not equal to" and && for "AND"
while (toEnd != "no" && toEnd != "yes") {
toEnd = prompt("Please enter a value of yes or no");
}
//I think you want to assign the value of toEnd to endProgram
// Note the the below is not the only/best way to do it
if(toEnd == "no") {
endProgram = false;
} else if(toEnd == "yes") {
endProgram = true;
}
// While use brackets not End s
// End While
// End While
}//End while loop here
}
Javascript in a browser cannot alter files - writeToFile, readFromFile have all been removed
I believe you want months to be global, if it is then initMonths is unnecessary
getNotGreen:
function getNotGreen(){
//You don't need to specify types in Javascript
/*Integer*/ var counter = 0
while (counter < 6){ //lowercase while
//I'm assuming you want to combine the values of "Enter NOT GREEN energy costs for" and months[counter] - This is done by using the + sign
//Im also assuming you want to read the value into notGreenCost
//.push adds a value to a array
notGreenCost.push(prompt("Enter NOT GREEN energy costs for" + months[counter]))
//Returning here makes the rest of the function redundant
//}
//return notGreenCost[counter];
//}
//Javascript does not use Set
// Note that below is not the only/best way to do it
/*Set*/ counter = counter + 1
} //End the while loop here
}
getGoneGreen:
function getGoneGreen(){
//Counter should probably be local (not global) - use var
var counter = 0;
while (counter < 6){//lowercase while
//I'm assuming you want to combine the values of "Enter NOT GREEN energy costs for" and months[counter] - This is done by using the + sign
//Im also assuming you want to read the value into notGreenCost
//.push adds a value to a array
goneGreenCost.push(prompt("Enter GONE GREEN energy costs for" + months[counter]));
//See above (getNotGreen)
//}
//return goneGreenCost[counter];
/*Set*/ counter = counter + 1;
}//End while loop here
}
energySaved:
function energySaved(){
//Counter should probably be local (not global) - use var
var counter = 0;
while (counter < 6){//lowercase while
savings[counter] = notGreenCost[counter] - goneGreenCost[counter]
counter = counter + 1;
}
} //I assume you want to end energySaved here?
displayInfo:
function displayInfo(){
//Alert produced individual boxes, i assume you want the following in a single window?
// "\n" is a line break
alert("SAVINGS NOT GREEN GONE GREEN MONTH\n"+
"_________________________________________________\n");
//Counter should probably be local (not global) - use var
var counter = 0;
while (counter < 6){//lowercase while
alert( "$" + savings[counter] + "$" + notGreenCost[counter] + "$" + goneGreenCost[counter] + "" + months[counter]);
counter = counter + 1;
}
} //I assume you want to end displayInfo here?
I'm having trouble with this code. I've tried to troubleshoot it many times and seem to have isolated the issue, but can't figure out the cause.
If the variable called string is set to something in the form of "text v. text," the code runs fine and the first if-statement triggers the sentence. If the string contains text but no "v." i.e. nothing that meets the search separator value, the function fails and does not execute the second if-statement.
Link to Fiddle: http://jsfiddle.net/qsq4we99/
Snippet of code, there also would need to be a html div with ID "outputtext."
function brokenCode()
{
//Setting Relevant Variables
var string = "red";
var array = string.split("v.");
var number = array.length;
// Checking location of things
var findText1 = array[0].search("search text");
var findText2 = array[1].search("search text");
//Running Conditional Stuff
if(number > 1)
{
document.getElementById('outputtext').innerHTML = "2+ listed";
}
else if(number < 2)
{
document.getElementById('outputtext').innerHTML = "1 listed";
}
}
brokenCode();
In this simplified example there is no clear explanation why the search operations need to occur (they are there because in the real code they are needed... but something about them seems to be causing the problem (even in this simple example). If the two searches are removed, the code runs smoothly.
You can't start setting variables from the array without checking for length. Before setting findText1 & findText2, check to make sure the length of the array is greater than zero.
function brokenCode() {
//Setting Relevant Variables
var string = "red";
var array = string.split("v.");
var number = array.length;
if (number > 0) {
// Checking location of things
var findText1 = array[0].search("search text");
var findText2 = array[1].search("search text");
//Running Conditional Stuff
if(number > 1)
{
document.getElementById('outputtext').innerHTML = "2+ listed";
}
else if(number < 2)
{
document.getElementById('outputtext').innerHTML = "1 listed";
}
}
}
brokenCode();
I'm trying to make hangman in javascript and I want to check if the user has used a letter already. I made a var letterGuessValue = to 0 and if they add an input it = 1. I know this would say know to everything if i got it to work (it doesn't even do anything) but am I on the right track maybe? Here's my code. http://jsbin.com/aWOnAfe/5/edit
I would say add an input to a list and whenever they add another input (aka letter), check this list to see if it is already in there. If it is, then its because they've already used that letter before. If not, then it is a new letter.
I don't see where the difficult part is.
http://jsfiddle.net/DerekL/jgqQ9/
Sample code
var used = {};
$("input").keyup(function(){
var val = this.value;
alert( used[val] ? "Used" : "Not used" );
this.value = "";
used[val] = true;
});
How it works
Assign true to used.LETTER when a letter is entered. Before assigning it though, if it was undefined then it hasn't been used. If it is true then it is used.
Sometimes developers tend to use an Array to record pressed keystrokes when doing key combinations, but in this case, iterating an Array would require both more memory and computation power. A simple object is an enough fit.
Use an array to store all of the used letters and function like this to add new ones.
var inputs = []
function addLetter(letter){
var used = false;
for(var i = 0; i < inputs.length; i++){
if(inputs[i] == letter){
used = true;
break;
}
}
if(!used){
inputs.push(letter);
}
}
The easiest way is to append each letter to a string, like this:
var letters = '';
var letterPressed = 'X'; // uppercase it if appropriate for your language
if (letters.indexOf(letterPressed) > -1)
{
// you already pressed it
}
else
{
letters += letterPressed;
}
You can also use an array to store your list of presses, although IMO that's overkill.
function checkData() {
var temp = 0;
var totalMarks = countMark(temp);
if (totalMarks != 100)
window.alert("Marks must total 100");
}
function countMark(mark) {
var totalMark = 0;
totalMark += parseInt(mark)
return totalMark;
}
function doAdd() {
var taskid = document.getElementById("taskid").value;
var taskname = document.getElementById("taskname").value;
var taskmark = document.getElementById("taskmark").value;
if (taskid.length === 0)
window.alert("Task Id cannot be empty!");
if (taskname.length === 0)
window.alert("Task name cannot be empty!");
if (taskmark.length === 0)
window.alert("Task Mark cannot be empty!");
else if (!markpattern.test(taskmark))
window.alert("Invalid data in mark field");
var marks = parseInt(document.getElementById("taskmark"));
if (marks < 0 || marks > 100)
window.alert("Marks out of range. Please re-enter");
countMark(marks);
}
My question is when i keep call the doAdd() function. my marks will keep adding . want to do like passing reference like in C++ . my function countMark(...) will keep adding .
after that, when my form submitted, my form will call the function checkData()
If my totalmark is not 100 . will prompt out the alert and error.
but my code is not working . I guess that my countMark function wrong somewhere
If I understand you correctly, you're looking for the equivalent of a static variable - something that gets initialized the first time the function is called, and keeps it's value for subsequent calls.
Take a look at this related question: https://stackoverflow.com/a/1535650/2444111
The top answer (by CMS) is talking about class-based static variables, which are not quite the same thing.
The second answer (by Pascal MARTIN) is what you're looking for. It takes advantage of the fact that JS functions are also objects, and stores the variable as a property of the function object. This is a better solution than using a global variable (or a property of window, which is what a global actually is)
There are several issues in your code and it's really hard to say what your intention was. But I will address what I found.
In the following piece of code you are requesting a DOM Element and try to parse it as an Integer. The result of that type convertion is always NaN. Maybe wanted to get the value attribute of your element, like you did before. (Also, don't request the same element multiple times. Request it once, save the result in a variable and use that variable from that on).
var marks = parseInt(document.getElementById("taskmark"));
if (marks < 0 || marks > 100)
window.alert("Marks out of range. Please re-enter");
countMark(marks);
Your function countMark is pretty useless, because it will always return whatever Number you pass to it (see comments in your code).
function countMark(mark) {
var totalMark = 0; //create a new variable with value 0
totalMark += parseInt(mark) //add "mark" to that variable
return totalMark; //return that variable => 0 + mark = mark (and if mark = NaN => 0 + mark = NaN)
}
Maybe you wanted to make totalMark a global variable, than you would need to define it outside of your function:
var totalMark = 0;
function countMark(mark) {
totalMark += parseInt(mark);
return totalMark;
}
Last but not least, lets analyse your function checkData:
function checkData() {
var temp = 0; //create a local variable with value 0
var totalMarks = countMark(temp); //pass 0 to countMark => return 0 => totalMarks = 0
if (totalMarks != 100) //always true since totalMarks is always 0
window.alert("Marks must total 100"); //will always alert
}