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Restrict input field

How to I restrict a number entering into input field (numeric) greater than another number using JavaScript?
I used:
function numberalert(e) {
var matrictotal = document.getElementById("matrictotal").value;
var matricobtained = document.getElementById("matricobtained").value;
var intertotal = document.getElementById("intertotal").value;
var interobtained = document.getElementById("interobtained").value;
var bachelortotal = document.getElementById("bachelortotal").value;
var bachelorobtained = document.getElementById("bachelorobtained").value;
var mphilltotal = document.getElementById("mphilltotal").value;
var mphillobtained = document.getElementById("mphillobtained").value;
if (matricobtained > matrictotal || interobtained > intertotal || bachelorobtained > bachelortotal || mphillobtained > mphilltotal) {
alert("pleses provide obtained marks less then total marks");
e.returnValue = false;
e.preventDefault();
} else {
return true;
}
}
But after alert it allows number place in input field.

First, just get the object that represents each object then pass in the two methods into a helped method to do the actual comparison. If the values are not what you are looking for, then set the objects value to "" and highlight the textbox to show which one is wrong.
function numberalert(e) {
var matrictotal = document.getElementById("matrictotal");
var matricobtained = document.getElementById("matricobtained");
var intertotal = document.getElementById("intertotal");
var interobtained = document.getElementById("interobtained");
var bachelortotal = document.getElementById("bachelortotal");
var bachelorobtained = document.getElementById("bachelorobtained");
var mphilltotal = document.getElementById("mphilltotal");
var mphillobtained = document.getElementById("mphillobtained");
checkValue(matrictotal, matricobtained);
checkValue(intertotal, interobtained);
checkValue(bachelortotal, bachelorobtained);
checkValue(mphilltotal, mphillobtained);
}
function checkValue(total, obtained){
if (obtained.value > total.value) {
alert("Please provide obtained marks less then total marks: " + obtained.id);
obtained.value = "";
obtained.classList.add("error");
} else {
obtained.classList.remove("error");
return true;
}
}
.error {
border: 2px solid #FF0000;
}
<label for="matrictotal">matrictotal</label>
<input type="text" id="matrictotal" value="10">
<label for="matricobtained">matricobtained</label>
<input type="text" id="matricobtained" value="10">
<br />
<label for="intertotal">intertotal</label>
<input type="text" id="intertotal" value="10">
<label for="interobtained">interobtained</label>
<input type="text" id="interobtained" value="10">
<br />
<label for="bachelortotal">bachelortotal</label>
<input type="text" id="bachelortotal" value="10">
<label for="bachelorobtained">bachelorobtained</label>
<input type="text" id="bachelorobtained" value="10">
<br />
<label for="mphilltotal">mphilltotal</label>
<input type="text" id="mphilltotal" value="10">
<label for="mphillobtained">mphillobtained</label>
<input type="text" id="mphillobtained" value="10">
<button onclick=numberalert(this)>Check values</button>

Note : In Javascript there is no strictly greater than or strictly less than comparator .
In case if you need strictly greater than use
(a !==b && a > b) (or) (!(a < b))
Similarly for strictly less than use
(a !== b && a < b) (or) (!(a>b))
var toCheckNumber = 100;
validate = function(el, event) {
var errorText = document.getElementById('errorText');
errorText.innerHTML = "";
var x = event.which;
var value = el.value;
var number = 0;
switch (x) {
case 48: number =0;break;
case 49: number = 1; break;
case 50: number = 2; break;
case 51: number = 3; break;
case 52: number = 4; break;
case 53: number = 5; break;
case 54: number = 6; break;
case 55: number = 7; break;
case 56: number = 8; break;
case 57: number = 9; break;
case 8: number = -1; break;
case 46: number = -1; break;
default : event.preventDefault(); return ;
}
var tempval = (number !== -1) ? value * 10 + number : value;
if (!(tempval < toCheckNumber)) {
event.preventDefault();
errorText.innerHTML = "Enter number less than " + toCheckNumber;
}
}
<input type="number" onkeydown="validate(this,event)" onchange="document.getElementById('errorText').innerHTML=''">
<div id="errorText" style="color:red"></div>

change() jQuery not working

I'm having some trouble getting my change() event working in jQuery. I am making a small program that converts temperatures to Kelvin, and I want the span that holds my value after conversion to update 1) every time the temperature to convert changes and 2) every time a different temperature scale is selected from the radio buttons.
Relevant Code:
$(document).ready(function() {
$('input[type=radio]').checkboxradio();
var temp = parseFloat()
$('input.listener').change(function() {
var name = $(this).attr("name");
var val = $(this).val();
switch (name) {
case 'unit':
var temperature = $('input#temp').val();
switch (val) {
case 'f':
$('span#output').html(((temperature - 32) / 1.8) + 273.15);
break;
case 'c':
$('span#output').html(temperature + 273.15);
break;
case 'r':
$('span#output').html(temperature / 1.8);
break;
}
case 'temp':
var u = $('input[name=unit]:checked').val();
switch (u) {
case 'f':
$('span#output').html(((val - 32) / 1.8) + 273.15);
break;
case 'c':
$('span#output').html(val + 273.15);
break;
case 'r':
$('span#output').html(val / 1.8);
break;
}
}
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="widget">
<fieldset>
<legend>Select a Unit to Convert to Kelvin: </legend>
<label for="fRadio">Fahrenheit</label>
<input id="fRadio" class="listener" type="radio" name="unit" value="f">
<label for="cRadio">Celsius</label>
<input id="cRadio" class="listener" type="radio" name="unit" value="c">
<label for="rRadio">Rankine</label>
<input id="rRadio" class="listener" type="radio" name="unit" value="r">
</fieldset>
</div>
<h2>Temperature Converter</h2>
<p>Type a value in the Fahrenheit field to convert the value to Kelvin:</p>
<p>
<label>Temperature</label>
<input id="temp" class="listener" type="number" value="32">
</p>
<p>Kelvin: <span id="output"></span></p>
My guess is I'm making a pretty dumb small mistake, but I can't seem to figure it out. Thanks for any and all help, suggestions, and solutions.

Two mistakes with your code:
Forgetting breaks; for the parent switch statement.
Forgetting name="temp" on the temperature field.
I changed the final temperature to a variable and made that the text of the output just so that there would be so many $('span#output').html(temperature);
Also, you should use the oninput event to detect a change for the number field.
$(document).ready(function() {
//$('input[type=radio]').checkboxradio();
var temp = parseFloat();
$('input.listener').on('change', updateTemp);
$('input.listener').on('input', updateTemp);
function updateTemp() {
var name = $(this).attr("name");
var val = $(this).val();
var final;
switch (name) {
case 'unit':
var temperature = $('input#temp').val();
switch (val) {
case 'f':
final = ((temperature - 32) / 1.8) + 273.15;
break;
case 'c':
final = temperature + 273.15;
break;
case 'r':
final = temperature / 1.8;
break;
}
break;
case 'temp':
var u = $('input[name=unit]:checked').val();
switch (u) {
case 'f':
final = ((val - 32) / 1.8) + 273.15;
break;
case 'c':
final = val + 273.15;
break;
case 'r':
final = val / 1.8;
break;
}
break;
}
$("#output").text(final);
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="widget">
<fieldset>
<legend>Select a Unit to Convert to Kelvin: </legend>
<label for="fRadio">Fahrenheit</label>
<input id="fRadio" class="listener" type="radio" name="unit" value="f">
<label for="cRadio">Celsius</label>
<input id="cRadio" class="listener" type="radio" name="unit" value="c">
<label for="rRadio">Rankine</label>
<input id="rRadio" class="listener" type="radio" name="unit" value="r">
</fieldset>
</div>
<h2>Temperature Converter</h2>
<p>Type a value in the Fahrenheit field to convert the value to Kelvin:</p>
<p>
<label>Temperature</label>
<input id="temp" class="listener" type="number" name="temp" value="32">
</p>
<p>Kelvin: <span id="output"></span></p>

You should set one of the radio buttons as default with checked="checked". Then try following:
$(document).ready(function () {
$('input.listener').change(function () {
if ($(this).attr("type") == 'radio') {
//radio button changed
var u = $(this).val();
} else {
var u = $("input[type='radio']:checked").val();
}
var temperature = $('#temp').val();
switch (u) {
case 'f':
$('span#output').html(((temperature - 32) / 1.8) + 273.15);
break;
case 'c':
$('span#output').html(temperature + 273.15);
break;
case 'r':
$('span#output').html(temperature / 1.8);
break;
}
});
});

You do not have break; after
case 'unit':
and when var name = "temp"
var val = $(this).val();
the value of var val above would be a number in string format, so when you do val + something in case 'temp' the number is getting appended instead getting added or substracted. Use parseInt(val) to convert the value of input box to integer in case of 'temp'.

Using radio buttons for a calculator

I am trying to make a simple calculator using radio buttons to select addition, subtraction, multiplication or division. However it is not working. I have tried a lot of things and googled it a lot, but I can't find out the issue. If anyone finds a problem with what I have, could you please give me a solution. Thanks!
<html>
<head>
<script language="javascript">
function operation() {
var ans =document.getElementById("answer").value;
if (document.getElementById("add").value = "add") {
ans= calculate(add);
}
if (document.getElementById("subtract").value = "subtract") {
ans= calculate(subtract);
}
if (document.getElementById("multiply").value = "multiply") {
ans= calculate(multiply);
}
if (document.getElementById("divide").value = "divide") {
ans= calculate(divide);
}
}
function calculate(action){
var num1 = document.getElementById("num1").value;
var num2 = document.getElementById("num2").value;
var result;
switch(action){
case add:
result= parseInt(num1)+parseInt(num2);
break;
case subtract:
result= num1-num2;
break;
case multiply:
result= num1*num2;
break;
case divide:
result= num1/num2;
break;
}
return result;
</script>
<title>
Calculator
</title>
</head>
<body>
<form>
<input type="text" id="num1">
+<input type="radio" name="group1" id="add" value="add">
-<input type="radio" name="group1" id="subtract" value="subtract">
*<input type="radio" name="group1" id="multiply" value="multiply">
/<input type="radio" name="group1" id="divide" value="divide">
<input type="text" id="num2">
=
<input type="text" id="answer" readonly>
<input type="button" value="Calculate" onClick="calculate()">
</form>
</body>
</html>

Your calculate function takes an argument:
function calculate(action){}
You are calling it without passing any paremeters:
<input type="button" value="Calculate" onClick="calculate()">
actually, i made this FIDDLE as the answer for someone's question few days ago. Is this some sort of homework?
function operation() {
var ans =document.getElementById("answer");
if (document.getElementById("add").checked) {
ans.value= calculate('add');
}
if (document.getElementById("subtract").checked) {
ans.value= calculate('subtract');
}
if (document.getElementById("multiply").checked) {
ans.value= calculate('multiply');
}
if (document.getElementById("divide").checked) {
ans.value= calculate('divide');
}
}
function calculate(action){
var num1 = document.getElementById("num1").value;
var num2 = document.getElementById("num2").value;
var result;
switch(action){
case 'add':
result= parseInt(num1)+parseInt(num2);
break;
case 'subtract':
result= num1-num2;
break;
case 'multiply':
result= num1*num2;
break;
case 'divide':
result= num1/num2;
break;
}
return result;
}
fiddle

You're not putting the result back into the answer box. You can return the value, but you have to tell it what text element to use.
document.getElementById("answer").value = ans;
In your if statements... "=" means assignment. "==" is comparison.
You have set the "value" of each radio button to something. So, you're checking if the value for "add" is "add", but you have already explicitly set the value to "add". Radio buttons are boolean: true or false.
function op() {
var ans = 0;
if (document.getElementById("add").value) {
ans= calculate(add);
} else if (document.getElementById("subtract").value) {
ans= calculate(subtract);
} else if (document.getElementById("multiply").value) {
ans= calculate(multiply);
} else if (document.getElementById("divide").value) {
ans= calculate(divide);
}
document.getElementById("answer").value = ans;
}
function calculate(action){
var num1 = document.getElementById("num1").value;
var num2 = document.getElementById("num2").value;
var result;
switch(action){
case add:
result= parseInt(num1)+parseInt(num2);
break;
case subtract:
result= num1-num2;
break;
case multiply:
result= num1*num2;
break;
case divide:
result= num1/num2;
break;
}
return result;
}
<input type="button" value="Calculate" id="b" onclick="op();">

You are looking at the values of buttons to see if they are active. They will always have the value that is assigned to them whether they are checked or not.
if (document.getElementById("add").value = "add") {
...when you should be checking to see if they're checked.
if (document.getElementById("add").getAttribute("checked") == "checked") {
Also, in JavaScript "==" is used for comparison, "=" is used to assign a value.

Getting value of a form doesn't work

My task is checking what an user keys in. If he keys in "Mars", he gets the value.
PLanet: <input type="text" id="form_1">
<input type="submit" onClick="send()" value="Send">
<script>
var planetEntered = document.getElementById('form_1').value;
var plantesLength = new Array(3);
plantesLength['Mars'] = 52;
plantesLength['Venera'] = 30;
plantesLength['Earth'] = 10;
plantesLength['Merkyriy'] = 60;
alert(plantesLength['Merkyriy']);
function send() {
switch(form_1) {
case 'Mars':
alert(plantesLength['Mars']);
break;
case 'Venera':
alert(plantesLength['Venera']);
break;
case 'Earth':
alert(plantesLength['Earth']);
break;
case 'Merkyriy':
alert(plantesLength['Merkyriy']);
break;
default:
alert("К сожалению, мы не нашли ни одну программу.");
break;
}
}
The function returns default-block. How to fix? Thanks.

try this
you have to get the input values inside the send function.
Demo Link http://jsbin.com/ejaSUTiH/1/
PLanet: <input type="text" id="form_1">
<input type="submit" onClick="send()" value="Send">
<script>
var plantesLength = new Array(3);
plantesLength['Mars'] = 52;
plantesLength['Venera'] = 30;
plantesLength['Earth'] = 10;
plantesLength['Merkyriy'] = 60;
alert(plantesLength['Merkyriy']);
function send() {
var planetEntered = document.getElementById('form_1').value;
console.log(planetEntered);
switch(planetEntered) {
case 'Mars':
alert(plantesLength['Mars']);
break;
case 'Venera':
alert(plantesLength['Venera']);
break;
case 'Earth':
alert(plantesLength['Earth']);
break;
case 'Merkyriy':
alert(plantesLength['Merkyriy']);
break;
default:
alert("К сожалению, мы не нашли ни одну программу.");
break;
}
}
</script>

You've to declare a variable inside the function send(): And set
planetEntered in switch case for checking:
function send() {
var planetEntered = document.getElementById('form_1').value; // Here
switch(planetEntered) { // Change
}
}
JS Fiddle Demo

You don't assign the value of the input box in the send() method so it's value is the default (empty) when send() is called.

Result is not showing

<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
var result = document.getElementById('answer').value;
if (document.getElementById('add')) {
function myFunction() {
add1 = document.getElementById('num1').value;
add2 = document.getElementById('num2').value;
ans = (parseInt(add1)+parseInt(add2));
result.innerHTML = ans;
}
}
</script>
</head>
<body>
<input type="text" id="num1" />
<select id="problem">
<option id="add">+</option>
<option id="sub">-</option>
<option id="mul">x</option>
<option id="div">÷</option>
</select>
<input type="text" id="num2" />
<br />
<input type="submit" onclick="myFunction();" />
<br />
<input type="text" id="answer" readonly />
</body>
</html>
I'm trying to make a sum solver by taking the values from the two text boxes and after clicking the button, it should post the result in the text box below. However it is not doing that.
I also want the program to change how a problem is solved using the dropdown menu with the mathematical symbols.
Thanks.

I think you're after something like this
function myFunction() {
var result = document.getElementById('answer'),
operator = document.getElementById('problem').value,
add1 = document.getElementById('num1').value,
add2 = document.getElementById('num2').value,
ans = 0;
switch (operator) {
case '+':
ans = (parseInt(add1) + parseInt(add2));
break;
case '-':
ans = (parseInt(add1) - parseInt(add2));
break;
case 'x':
ans = (parseInt(add1) * parseInt(add2));
break;
case '÷':
ans = (parseInt(add1) / parseInt(add2));
break;
}
result.value = ans;
}
instead of using if statements, and creating different functions, just have one function and determine the operand.
Edit: Also, watch out for your variable declarations. 'ans', 'add1' and 'add2' weren't being declared which resulted in global variables being created

The problem should be with the line
var result = document.getElementById('answer').value;
Try the below snippet
var result=document.getElementById('answer');
ans = (parseInt(add1)+parseInt(add2));
result.value=ans;
http://jsfiddle.net/2W5za/1/

You have a few issues. Not sure what you were going for with the if but remove it. Also, set the value of a textbox with value not innerHTML.
function myFunction() {
var result = document.getElementById('answer');
add1 = document.getElementById('num1').value;
add2 = document.getElementById('num2').value;
ans = (parseInt(add1)+parseInt(add2));
result.value = ans;
}
http://jsfiddle.net/LjqMJ/

Regarding the first part of the question (and that for which this question is titled), one problem I see is this line of code right here:
var result = document.getElementById('answer').value;
What is the type of result? Later on you treat it as if it is a DOMElement with result.innerHTML = ans; by assuming it has a property innerHTML. However because you used .value it's in fact a string which will not have innerHTML.
Regarding the second part, you can assert which function is selected in the <select> by looking at it's .value. The <option> tags will always exist, regardless of if they are selected or not.
Speaking more broadly, I highly recommend you check out using the debugger in either chrome or firefox. That will allow you to drop a breakpoint in your code, and figure out if the value is being computed correctly, and see what it is attempting to write to, all interactively.
Chrome:
https://developers.google.com/chrome-developer-tools/docs/javascript-debugging
Firefox:
https://developer.mozilla.org/en-US/docs/Tools/Debugger

<!DOCTYPE html>
<html>
<head></head>
<body>
<input type="text" id="num1" />
<select id="problem">
<option value="add">+</option>
<option value="sub">-</option>
<option value="mul">x</option>
<option value="div">%</option>
</select>
<input type="text" id="num2" />
<br />
<input type="submit" onclick="myFunction();" />
<br />
<input type="text" id="answer" readonly />
<script type="text/javascript">
function myFunction()
{
var e = document.getElementById("problem");
var sOperation = e.options[e.selectedIndex].value;
add1 = document.getElementById('num1').value;
add2 = document.getElementById('num2').value;
var ans;
if (!isNaN(add1) && !isNaN(add2)){
if(sOperation=='add'){
//Add
ans = parseInt(add1)+parseInt(add2);
} else if (sOperation=='sub') {
//Subtract
ans = parseInt(add1)-parseInt(add2);
} else if (sOperation=='mul') {
//Multiple
ans = parseInt(add1) * parseInt(add2);
} else if (sOperation=='div') {
//Divide
ans = parseInt(add1) / parseInt(add2);
}
document.getElementById("answer").value = ans;
} else {
alert("Please enter numeric values only");
return false;
}
}

There are many things wrong with your code. However, to fix your problem, change = ans to = ans.toString();
You see, in javascript integers and strings cannot change to each other's values without a conversion (kind of like a brother and sister refusing to share), so toString() is used for a conversion to String.
The other thing to change is innerHTML to value, because you are dealing with text boxes.

HTML
<input type="text" id="num1" />
<select id="problem">
<option id="add">+</option>
<option id="sub">-</option>
<option id="mul">x</option>
<option id="div">÷</option>
</select>
<input type="text" id="num2" />
<br />
<input type="submit" onclick="myFunction();" />
<br />
<input type="text" id="answer" readonly />
JavaScript
function myFunction() {
var result = document.getElementById('answer');
var operator = document.getElementById('problem').value;
var add1 = document.getElementById('num1').value;
var add2 = document.getElementById('num2').value;
var ans;
if (!isNaN(add1) && !isNaN(add2)) {
//Addition
if (operator == '+')
{
ans = (parseInt(add1) + parseInt(add2));
}
//Subtraction
else if (operator == '-') {
ans = (parseInt(add1) - parseInt(add2));
}
//Multiplication
else if (operator == 'x') {
ans = (parseInt(add1) * parseInt(add2));
}
//Division
else if (operator == '÷') {
ans = (parseInt(add1) / parseInt(add2));
}
//Result
result.value = ans;
} else {
alert("Please enter numeric values only");
return false;
}
}
Fiddle Demo