Develop Reference

Javascript looping through Page elements to change states?

This is relatively simple, but I'm missing something. I have 10 checkboxes on a page, in a table in a form. They all have names and id's of add0, add1, add2, etc. I wanted to build a "check/uncheck all" checkbox, but my code doesn't seem to be working. On firefox, using firebug, but it can't seem to follow the script execution.
function checkboxprocess(current)
{
for (i = 0; i < 10; i++)
{
if (current.checked)
{
document.getElementById("add" + i).checked = true;
}
else
{
document.getElementById("add" + i]).checked = false;
}
}
}
Checkbox:
echo "Select All: <input type=\"checkbox\" name=\"add\" id=\"add\" value=1 onChange=\"checkboxprocess(this)\"><br>";

You have extra ] in your code:
document.getElementById("add" + i]).checked = false;
And you don't have to check if is current checked each time in the loop, you can do it easily like this:
function checkboxprocess(current) {
for (i = 0; i < 10; i++) {
document.getElementById("add" + i).checked = current.checked;
// current.checked will return true/false
}
}
<form>
Select All: <input type="checkbox" onChange="checkboxprocess(this)">
<br /> <br />
<input type="checkbox" id="add0">
<input type="checkbox" id="add1">
<input type="checkbox" id="add2">
<input type="checkbox" id="add3">
<input type="checkbox" id="add4">
<input type="checkbox" id="add5">
<input type="checkbox" id="add6">
<input type="checkbox" id="add7">
<input type="checkbox" id="add8">
<input type="checkbox" id="add9">
</form>

Creating a multiple choice option in javascript

I have created an HTML multiple choice question. I am facing a problem how to validate it. Below is the HTML code:
<h1>JavaScript is ______ Language.</h1><br>
<form>
<input type="radio" name="choice" value="Scripting"> Scripting
<input type="radio" name="choice" value="Programming"> Programming
<input type="radio" name="choice" value="Application"> Application
<input type="radio" name="choice" value="None of These"> None of These
</form>
<button>Submit Answer</button>
When the user clicks the submit button, there should be an alert that will show a message based on what was selected.
If no option was selected, the alert box should say "please select choice answer".
If the "Scripting" option was selected, the alert box should say "Answer is correct !"
If an option different from "Scripting" is selected, the alert box should say "Answer is wrong".
I want to create this validation in JavaScript.

You have to use onclick attribute and more js
attach event hander to your button
get radio elements value
compare
var submitAnswer = function() {
var radios = document.getElementsByName('choice');
var val= "";
for (var i = 0, length = radios.length; i < length; i++) {
if (radios[i].checked) {
val = radios[i].value;
break;
}
}
if (val == "" ) {
alert('please select choice answer');
} else if ( val == "Scripting" ) {
alert('Answer is correct !');
} else {
alert('Answer is wrong');
}
};
<h1>JavaScript is ______ Language.</h1><br>
<form >
<input type="radio" name="choice" value="Scripting"> Scripting
<input type="radio" name="choice" value="Programming"> Programming
<input type="radio" name="choice" value="Application"> Application
<input type="radio" name="choice" value="None of These"> None of These
</form>
<button onclick="submitAnswer()">Submit Answer</button>

var submitAnswer = function() {
var radios = document.getElementsByName('choice');
var val= "";
for (var i = 0, length = radios.length; i < length; i++) {
if (radios[i].checked) {
val = radios[i].value;
break;
}
}
if (val == "" ) {
alert('please select choice answer');
} else if ( val == "Scripting" ) {
alert('Answer is correct !');
} else {
alert('Answer is wrong');
}
};
<h1>JavaScript is ______ Language.</h1><br>
<form >
<input type="radio" name="choice" value="Scripting"> Scripting
<input type="radio" name="choice" value="Programming"> Programming
<input type="radio" name="choice" value="Application"> Application
<input type="radio" name="choice" value="None of These"> None of These
</form>
<button onclick="submitAnswer()">Submit Answer</button>
Some changes
I made some changes to the code above to make it more 'abstract'
<h1>JavaScript is ______ Language.</h1><br>
<form id="d1">
<input type="radio" name="choice" value="Scripting"> Scripting
<input type="radio" name="choice" value="Programming"> Programming
<input type="radio" name="choice" value="Application"> Application
<input type="radio" name="choice" value="None of These"> None of These
</form>
<button onclick="submitAnswer(d1.choice.value, 'Scripting')">Submit Answer</button>
<script>
var submitAnswer = function(valore, rightanswer) {
if (valore == rightanswer) {
alert("OK");
}
};
</script>
Another, more complex example
<div style="background-color:lightblue">
<h1>JavaScript is a <span id='a1'>______</span> Language.</h1><br>
<form id="d1">
<input type="radio" name="choice" value="Scripting"> Scripting
<input type="radio" name="choice" value="Programming"> Programming
<input type="radio" name="choice" value="Application"> Application
<input type="radio" name="choice" value="None of These"> None of These
<br>
<input type="submit" value="submit" onclick="validate(choice.value, 'Scripting', 'd1','a1')">
</form>
</div>
<div style="background-color:lightblue">
<h1>Python is a <span id='a2'>______</span> Language.</h1><br>
<form id="d2">
<input type="radio" name="choice" value="Scripting"> Scripting
<input type="radio" name="choice" value="Wonderful"> Wonderful
<input type="radio" name="choice" value="Application"> Application
<input type="radio" name="choice" value="None of These"> None of These
<br>
<input type="submit" value="submit" onclick="validate(choice.value, 'Wonderful', 'd2', 'a2')">
</form>
</div>
<script>
var validate = function(valore, rightanswer, form, span) {
var formname = document.getElementById(form)
var spanname = document.getElementById(span)
spanname.innerHTML = rightanswer;
if (valore == rightanswer) {
formname.innerHTML ="<div style='background-color:lightgreen'><h1>GREAT! YOU'RE RIGHT: The answer, in fact, was: " + rightanswer + "</h1></div>";
}
else {
formname.innerHTML ="<div style='background-color:pink'><h1>Sorry, you where wrong: The answer was: " + rightanswer + "</h1></div>";
}
};
</script>

Use the required keyword. This prompts the user to choose a value, when the submit button is pressed without choosing any option. And always prefer to use
<input type="submit" value="submit"> over <button>Submit Answer</button>
while handling forms. Use the onclick() event handler to call your Javascript code.
<h1>JavaScript is ______ Language.</h1><br>
<form >
<input type="radio" name="choice" value="Scripting" required> Scripting
<input type="radio" name="choice" value="Programming"> Programming
<input type="radio" name="choice" value="Application"> Application
<input type="radio" name="choice" value="None of These"> None of These
<input type="submit" value="submit" onclick="validate()">
</form>
And the javascript part is as follows.
<script type="text/javascript">
function validate() {
var a= document.getElementByName("choice");
for (var i = 0, i < a.length; i++) {
if (a[i].checked) {
if( a[i].value == "scripting" )
alert("your answer is correct");
else
alert("your answer is not correct");
break;
} } }
</script>

Here condition is showing in alert pop up box. but I want to show it in a html tag.
But after clicking submit button, innerHTML content showing a millisecond and then automatic remove the content. How selection will stay in innerHTML
document.getElementById("answer").innerHTML;
var submitAnswer = function() {
var radios = document.getElementsByName('choice');
var val= "";
for (var i = 0, length = radios.length; i < length; i++) {
if (radios[i].checked) {
val = radios[i].value;
break;
}
}
if (val == "" ) {
document.getElementById("answer").innerHTML = "please select choice answer";
} else if ( val == "Scripting" ) {
document.getElementById("answer").innerHTML = "Answer is correct !"
} else {
document.getElementById("answer").innerHTML = "Answer is wrong"
}
};

You can add a function and event onClick so that whenever someone clicks on option submit button will appear.

Javascript form NAN error

Firstly I apologies, I've just starting out with JavaScript
I have a problem with a form. I have two groups of Radio buttons on the form (age and bmi)
Everytime the 'Calculate' button is clicked, I want add the values of each checked Radio button and alert this to the screen.
It works in Chrome, but ALL other browsers give an NAN error.
Can anyone help?
<br>
<input type="radio" name="age" class="myradioButton" value = "1"/>
<input type="radio" name="bmi" class="myradioButton" value = "3"/>
<input type="button" name="Calculate" id="calculate"onclick="calculatehealth()" value="Calculate"/>
<br>
<script>
function calculatehealth() {
var valueAge = document.forms['myForm'].elements["age"].value;
var valueint = parseInt(valueAge);
var valueBmi = document.forms['myForm'].elements["bmi"].value;
var Bmiint = parseInt(valueBmi);
var total = Bmiint + valueint;
alert(total);
}

Demo: http://jsfiddle.net/z4RKx/
HTML
<form id="myForm">
<input type="radio" name="age" class="myradioButton" value="1" />
<input type="radio" name="bmi" class="myradioButton" value="3" />
<input type="button" name="Calculate" value="Calculate" onclick='calculatehealth()' />
</form>
JS
function calculatehealth() {
var valueint = 0;
if (document.forms['myForm'].elements["age"].checked) {
valueint += parseInt(document.forms['myForm'].elements["age"].value);
}
if (document.forms['myForm'].elements["bmi"].checked) {
valueint += parseInt(document.forms['myForm'].elements["bmi"].value);
}
alert(valueint);
}
And if you have many elements this might be a good alternative:
function calculatehealth() {
var valueint = 0;
for(i = 0; i < document.forms['myForm'].elements.length; i++) {
if (document.forms['myForm'].elements[i].checked) {
valueint += parseInt(document.forms['myForm'].elements[i].value);
}
}
alert(valueint);
}

How to check if everything in the loop is true?

I have a simple multiple question form, each question has 4 answers and users must select 1 answer for each question.
So far I can check for an unanswered question and show an error message.
But now if all questions have been answered, I need the form to go to a results page (I assume window.location?)
How can I check if all questions have been answered?
$('.submit-button').click(function(event){
$('.validate-message').hide();
for (var i=1;i<6;i++) {
var input = $("input[name=q"+i+"]");
var inputChecked = $("input[name=q"+i+"]:checked");
if (!inputChecked.val()) { //if an answer is not selected for a question
$(input).parents('fieldset').append('<div class="validate-message" style="color:red;">Please choose an answer!</div>');
} else { // if an answer is selected for a question
}
}
return false;
});

Just use a boolean variable:
$('.submit-button').click(function(event){
var noErrors = true; // default to no errors
$('.validate-message').hide();
for (var i=1;i<6;i++) {
var input = $("input[name=q"+i+"]");
var inputChecked = $("input[name=q"+i+"]:checked");
if (!inputChecked.val()) { //if an answer is not selected for a question
noErrors = false; // an error was found, set noErrors to false
$(input).parents('fieldset').append('<div class="validate-message" style="color:red;">Please choose an answer!</div>');
} else { // if an answer is selected for a question
}
}
if(noErrors) // do stuff
return false;
});

Out of interest, here's a plain javascript solution.
Assuming HTML something like the following:
<form id="f0" onsubmit="return validateForm(this);">
<div>
<p>Question 1.<br>
A<input type="radio" value="A" name="q1"><br>
B<input type="radio" value="B" name="q1"><br>
C<input type="radio" value="C" name="q1"><br>
D<input type="radio" value="D" name="q1"><br>
</p>
<p>Question 2.<br>
A<input type="radio" value="A" name="q2"><br>
B<input type="radio" value="B" name="q2"><br>
C<input type="radio" value="C" name="q2"><br>
D<input type="radio" value="D" name="q2"><br>
</p>
<input type="reset" value="Clear answers">
<input type="submit" value="Submit answers">
</div>
</form>
A function to validate that each question has been answered is:
function validateForm(form) {
var control, controls = form.elements;
var visited = {};
var name, radios;
for (var i=0, iLen=controls.length; i<iLen; i++) {
control = controls[i];
name = control.name;
if (control.type == 'radio' && name && !visited.hasOwnProperty(name)) {
visited[name] = false;
radios = form[name];
for (j=0, jLen=radios.length; j<jLen; j++) {
visited[name] = visited[name] || radios[j].checked;
}
if (!visited[name]) {
// Question hasn't been answered, cancel submit and do whatever
alert('There are unanswered questions for ' + name);
return false;
}
}
// Validation for other controls
// ...
}
}

Adding form verification in this case

I've got 3 groups of radio buttons and 1 set of check boxes.
How do i check if a radio button is selected in each group of radio buttons and at least one check box is selected? And if not, maybe pop an alert window.
So thats : one radio button needs to be selected from all three groups and one check box (all four are mandatory). I've had no luck with this. Thanks
<html>
<head>
<script type="text/javascript">
function DisplayFormValues()
{
var str = '';
var elem = document.getElementById('frmMain').elements;
for(var i = 0; i < elem.length; i++)
{
if(elem[i].checked)
{
str += elem[i].value+"<br>";
}
}
document.getElementById('lblValues').innerHTML = str;
document.frmMain.reset();
}
</script>
</head>
<body>
<form id="frmMain" name="frmMain">
Set 1
<INPUT TYPE="radio" NAME="r1" value="r1a">
<INPUT TYPE="radio" NAME="r1" value="r1b">
<INPUT TYPE="radio" NAME="r1" value="r1c">
<br>
Set 2
<INPUT TYPE="radio" NAME="r2" value="r2a">
<INPUT TYPE="radio" NAME="r2" value="r2b">
<INPUT TYPE="radio" NAME="r2" value="r2c">
<br>
Set 3
<INPUT TYPE="radio" NAME="r3" value="r3a">
<INPUT TYPE="radio" NAME="r3" value="r3b">
<INPUT TYPE="radio" NAME="r3" value="r3c">
<br>
Check 1
<INPUT TYPE="checkbox" NAME="c1" value="c1a">
<INPUT TYPE="checkbox" NAME="c1" value="c1b">
<INPUT TYPE="checkbox" NAME="c1" value="c1c">
<input type="button" value="Test" onclick="DisplayFormValues();" />
</form>
<hr />
<div id="lblValues"></div>
</body>
</html>

Here's a modified version of your function:
function DisplayFormValues() {
var str = '';
var elem = document.getElementById('frmMain').elements;
var groups = { 'r1': 0, 'r2': 0, 'r3':0, 'c1': 0 };
for (var i = 0; i < elem.length; i++){
if (elem[i].checked) {
var n = elem[i].name;
groups[n] += 1
str += elem[i].value + "<br>";
}
}
document.getElementById('lblValues').innerHTML = groups['r1'] + "/" +
groups['r2'] + "/" + groups['r3'] + "/" + groups['c1'];
document.frmMain.reset();
}
In this function we count how many elements are checked (obviously one for radio button in the same group but you understand the principle and this is flexible) and groups[XXX] is the count (with XXX being the group name).
You can adjust to your needs and add the alert as requested.

You can do this in javascript by writing a lot of code or I strongly recommend using jquery validation plugin. Look at this example: http://jquery.bassistance.de/validate/demo/radio-checkbox-select-demo.html
You can do something like:
<input type="radio" validate="required:true" name="family" value="s" id="family_single" class="error">
Which will require at least one option being selected.
Also, its best to have inline feedback when something is not valid. Having alerts can be really annoying.

var radioCount = 0;
var checkBoxCount = 0;
var currentElement;
for (var i = 0; i < elem.length; ++i) {
currentElement = elem[i];
if (!currentElement.checked)
continue;
if (currentElement.type == "checkbox")
++checkBoxCount;
else if (currentElement.type == "radio")
++radioCount;
}
if (radioCount < 3)
//fail
if (checkBoxCount < 1)
//fail