simple javascript string calculator

simple javascript string calculator - javascript

I am trying to build a simple javascript calculator that will ask user to input name and it will display a number according to input, each letter in string will have a value like a=1 and b=2. If we insert acb in input it should display abc=1+2+3 =6.
thanks
<input type="text" id="myText" value="">
<button onclick="myFunction()">Try it</button>
<p id="calc"></p>
<script>
function myFunction() {
var x = document.getElementById("myText").value;
document.getElementById("calc").innerHTML = x;
}
</script>

Try this, it uses a simple a=1 to z=26 code. If a special character or number is entered, they are treated as 0. This does work for uppercase and lowercase letters.
function myFunction() {
var x = document.getElementById("myText").value;
var total = 0;
for (var i = 0; i < x.length; i++) {
var temp = x.toLowerCase().charCodeAt(i) - 96;
if ((temp > 0) & (temp < 27)) {
total = total + temp;
}
}
document.getElementById("calc").innerHTML = total;
}
<input type="text" id="myText" value="">
<button onclick="myFunction()">Try it</button>
<p id="calc"></p>

Related

JS weird += result [duplicate]

I am adding two numbers, but I don't get a correct value.
For example, doing 1 + 2 returns 12 and not 3
What am I doing wrong in this code?
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = y + z;
document.getElementById("demo").innerHTML = x;
}
<p>
Click the button to calculate x.
<button onclick="myFunction()">Try it</button>
</p>
<p>
Enter first number:
<input type="text" id="txt1" name="text1" value="1">
Enter second number:
<input type="text" id="txt2" name="text2" value="2">
</p>
<p id="demo"></p>

They are actually strings, not numbers. The easiest way to produce a number from a string is to prepend it with +:
var x = +y + +z;

I just use Number():
var i=2;
var j=3;
var k = Number(i) + Number(j); // 5

You need to use javaScript's parseInt() method to turn the strings back into numbers. Right now they are strings so adding two strings concatenates them, which is why you're getting "12".

Use parseInt(...) but make sure you specify a radix value; otherwise you will run into several bugs (if the string begins with "0", the radix is octal/8 etc.).
var x = parseInt(stringValueX, 10);
var y = parseInt(stringValueY, 10);
alert(x + y);
Hope this helps!

The following may be useful in general terms.
First, HTML form fields are limited to text. That applies especially to text boxes, even if you have taken pains to ensure that the value looks like a number.
Second, JavaScript, for better or worse, has overloaded the + operator with two meanings: it adds numbers, and it concatenates strings. It has a preference for concatenation, so even an expression like 3+'4' will be treated as concatenation.
Third, JavaScript will attempt to change types dynamically if it can, and if it needs to. For example '2'*'3' will change both types to numbers, since you can’t multiply strings. If one of them is incompatible, you will get NaN, Not a Number.
Your problem occurs because the data coming from the form is regarded as a string, and the + will therefore concatenate rather than add.
When reading supposedly numeric data from a form, you should always push it through parseInt() or parseFloat(), depending on whether you want an integer or a decimal.
Note that neither function truly converts a string to a number. Instead, it will parse the string from left to right until it gets to an invalid numeric character or to the end and convert what has been accepted. In the case of parseFloat, that includes one decimal point, but not two.
Anything after the valid number is simply ignored. They both fail if the string doesn’t even start off as a number. Then you will get NaN.
A good general purpose technique for numbers from forms is something like this:
var data=parseInt(form.elements['data'].value); // or parseFloat
If you’re prepared to coalesce an invalid string to 0, you can use:
var data=parseInt(form.elements['data'].value) || 0;

Just add a simple type casting method as the input is taken in text. Use the following:
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = y + z;

This won't sum up the number; instead it will concatenate it:
var x = y + z;
You need to do:
var x = (y)+(z);
You must use parseInt in order to specify the operation on numbers. Example:
var x = parseInt(y) + parseInt(z); [final soulution, as everything us]

Simple
var result = parseInt("1") + parseInt("2");
console.log(result ); // Outputs 3

This code sums both the variables! Put it into your function
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = (y +z);
document.getElementById("demo").innerHTML = x;`

<head>
<script type="text/javascript">
function addition()
{
var a = parseInt(form.input1.value);
var b = parseInt(form.input2.value);
var c = a+b
document.write(c);
}
</script>
</head>
<body>
<form name="form" method="GET">
<input type="text" name="input1" value=20><br>
<input type="text" name="input2" value=10><br>
<input type="button" value="ADD" onclick="addition()">
</form>
</body>
</html>

Or you could simply initialize
var x = 0; ( you should use let x = 0;)
This way it will add not concatenate.

If Nothing works then only try this. This maybe isn't Right way of doing it but it worked for me when all the above failed.
var1 - (- var2)

You are missing the type conversion during the addition step...
var x = y + z; should be var x = parseInt(y) + parseInt(z);
<!DOCTYPE html>
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction()
{
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = parseInt(y) + parseInt(z);
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>

<input type="text" name="num1" id="num1" onkeyup="sum()">
<input type="text" name="num2" id="num2" onkeyup="sum()">
<input type="text" name="num2" id="result">
<script>
function sum()
{
var number1 = document.getElementById('num1').value;
var number2 = document.getElementById('num2').value;
if (number1 == '') {
number1 = 0
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
else if(number2 == '')
{
number2 = 0;
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
else
{
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
}
</script>

It's very simple:
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = +y + +z;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>

Try this:
<!DOCTYPE html>
<html>
<body>
<p>Add Section</p>
<label>First Number:</label>
<input id="txt1" type="text"/><br />
<label>Second Number:</label>
<input id="txt2" type="text"/><br />
<input type="button" name="Add" value="Add" onclick="addTwoNumber()"/>
<p id="demo"></p>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = Date();
}
function addTwoNumber(){
var a = document.getElementById("txt1").value;
var b = document.getElementById("txt2").value;
var x = Number(a) + Number(b);
document.getElementById("demo").innerHTML = "Add Value: " + x;
}
</script>
</body>
</html>

If we have two input fields then get the values from input fields, and then add them using JavaScript.
$('input[name="yourname"]').keyup(function(event) {
/* Act on the event */
var value1 = $(this).val();
var value2 = $('input[name="secondName"]').val();
var roundofa = +value2+ +value1;
$('input[name="total"]').val(addition);
});

This can also be achieved with a more native HTML solution by using the output element.
<form oninput="result.value=parseInt(a.valueAsNumber)+parseInt(b.valueAsNumber)">
<input type="number" id="a" name="a" value="10" /> +
<input type="number" id="b" name="b" value="50" /> =
<output name="result" for="a b">60</output>
</form>
https://jsfiddle.net/gxu1rtqL/
The output element can serve as a container element for a calculation or output of a user's action. You can also change the HTML type from number to range and keep the same code and functionality with a different UI element, as shown below.
<form oninput="result.value=parseInt(a.valueAsNumber)+parseInt(b.valueAsNumber)">
<input type="range" id="a" name="a" value="10" /> +
<input type="number" id="b" name="b" value="50" /> =
<output name="result" for="a b">60</output>
</form>
https://jsfiddle.net/gxu1rtqL/2/

You can do a precheck with regular expression wheather they are numbers as like
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
if((x.search(/[^0-9]/g) != -1)&&(y.search(/[^0-9]/g) != -1))
var x = Number(y)+ Number(z);
else
alert("invalid values....");
document.getElementById("demo").innerHTML = x;
}

Use parseFloat it will convert string to number including decimal values.
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = parseFloat(y) + parseFloat(z);
document.getElementById("demo").innerHTML = x;
}
<p>
Click the button to calculate x.
<button onclick="myFunction()">Try it</button>
</p>
<p>
Enter first number:
<input type="text" id="txt1" name="text1" value="1">
Enter second number:
<input type="text" id="txt2" name="text2" value="2">
</p>
<p id="demo"></p>

You can also write :
var z = x - -y ;
And you get correct answer.
<body>
<input type="text" id="number1" name="">
<input type="text" id="number2" name="">
<button type="button" onclick="myFunction()">Submit</button>
<p id="demo"></p>
<script>
function myFunction() {
var x, y ;
x = document.getElementById('number1').value;
y = document.getElementById('number2').value;
var z = x - -y ;
document.getElementById('demo').innerHTML = z;
}
</script>
</body>

Here goes your code by parsing the variables in the function.
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">
<br>Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction() {
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = y + z;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>
Answer

An alternative solution, just sharing :) :
var result=eval(num1)+eval(num2);

Perhaps you could use this function to add numbers:
function calculate(a, b) {
return a + b
}
console.log(calculate(5, 6))

Why am I getting NaN when I enter numbers with decimals? [duplicate]

I am adding two numbers, but I don't get a correct value.
For example, doing 1 + 2 returns 12 and not 3
What am I doing wrong in this code?
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = y + z;
document.getElementById("demo").innerHTML = x;
}
<p>
Click the button to calculate x.
<button onclick="myFunction()">Try it</button>
</p>
<p>
Enter first number:
<input type="text" id="txt1" name="text1" value="1">
Enter second number:
<input type="text" id="txt2" name="text2" value="2">
</p>
<p id="demo"></p>

They are actually strings, not numbers. The easiest way to produce a number from a string is to prepend it with +:
var x = +y + +z;

I just use Number():
var i=2;
var j=3;
var k = Number(i) + Number(j); // 5

You need to use javaScript's parseInt() method to turn the strings back into numbers. Right now they are strings so adding two strings concatenates them, which is why you're getting "12".

Use parseInt(...) but make sure you specify a radix value; otherwise you will run into several bugs (if the string begins with "0", the radix is octal/8 etc.).
var x = parseInt(stringValueX, 10);
var y = parseInt(stringValueY, 10);
alert(x + y);
Hope this helps!

The following may be useful in general terms.
First, HTML form fields are limited to text. That applies especially to text boxes, even if you have taken pains to ensure that the value looks like a number.
Second, JavaScript, for better or worse, has overloaded the + operator with two meanings: it adds numbers, and it concatenates strings. It has a preference for concatenation, so even an expression like 3+'4' will be treated as concatenation.
Third, JavaScript will attempt to change types dynamically if it can, and if it needs to. For example '2'*'3' will change both types to numbers, since you can’t multiply strings. If one of them is incompatible, you will get NaN, Not a Number.
Your problem occurs because the data coming from the form is regarded as a string, and the + will therefore concatenate rather than add.
When reading supposedly numeric data from a form, you should always push it through parseInt() or parseFloat(), depending on whether you want an integer or a decimal.
Note that neither function truly converts a string to a number. Instead, it will parse the string from left to right until it gets to an invalid numeric character or to the end and convert what has been accepted. In the case of parseFloat, that includes one decimal point, but not two.
Anything after the valid number is simply ignored. They both fail if the string doesn’t even start off as a number. Then you will get NaN.
A good general purpose technique for numbers from forms is something like this:
var data=parseInt(form.elements['data'].value); // or parseFloat
If you’re prepared to coalesce an invalid string to 0, you can use:
var data=parseInt(form.elements['data'].value) || 0;

Just add a simple type casting method as the input is taken in text. Use the following:
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = y + z;

This won't sum up the number; instead it will concatenate it:
var x = y + z;
You need to do:
var x = (y)+(z);
You must use parseInt in order to specify the operation on numbers. Example:
var x = parseInt(y) + parseInt(z); [final soulution, as everything us]

Simple
var result = parseInt("1") + parseInt("2");
console.log(result ); // Outputs 3

This code sums both the variables! Put it into your function
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = (y +z);
document.getElementById("demo").innerHTML = x;`

<head>
<script type="text/javascript">
function addition()
{
var a = parseInt(form.input1.value);
var b = parseInt(form.input2.value);
var c = a+b
document.write(c);
}
</script>
</head>
<body>
<form name="form" method="GET">
<input type="text" name="input1" value=20><br>
<input type="text" name="input2" value=10><br>
<input type="button" value="ADD" onclick="addition()">
</form>
</body>
</html>

Or you could simply initialize
var x = 0; ( you should use let x = 0;)
This way it will add not concatenate.

If Nothing works then only try this. This maybe isn't Right way of doing it but it worked for me when all the above failed.
var1 - (- var2)

You are missing the type conversion during the addition step...
var x = y + z; should be var x = parseInt(y) + parseInt(z);
<!DOCTYPE html>
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction()
{
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = parseInt(y) + parseInt(z);
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>

<input type="text" name="num1" id="num1" onkeyup="sum()">
<input type="text" name="num2" id="num2" onkeyup="sum()">
<input type="text" name="num2" id="result">
<script>
function sum()
{
var number1 = document.getElementById('num1').value;
var number2 = document.getElementById('num2').value;
if (number1 == '') {
number1 = 0
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
else if(number2 == '')
{
number2 = 0;
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
else
{
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
}
</script>

It's very simple:
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = +y + +z;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>

Try this:
<!DOCTYPE html>
<html>
<body>
<p>Add Section</p>
<label>First Number:</label>
<input id="txt1" type="text"/><br />
<label>Second Number:</label>
<input id="txt2" type="text"/><br />
<input type="button" name="Add" value="Add" onclick="addTwoNumber()"/>
<p id="demo"></p>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = Date();
}
function addTwoNumber(){
var a = document.getElementById("txt1").value;
var b = document.getElementById("txt2").value;
var x = Number(a) + Number(b);
document.getElementById("demo").innerHTML = "Add Value: " + x;
}
</script>
</body>
</html>

If we have two input fields then get the values from input fields, and then add them using JavaScript.
$('input[name="yourname"]').keyup(function(event) {
/* Act on the event */
var value1 = $(this).val();
var value2 = $('input[name="secondName"]').val();
var roundofa = +value2+ +value1;
$('input[name="total"]').val(addition);
});

This can also be achieved with a more native HTML solution by using the output element.
<form oninput="result.value=parseInt(a.valueAsNumber)+parseInt(b.valueAsNumber)">
<input type="number" id="a" name="a" value="10" /> +
<input type="number" id="b" name="b" value="50" /> =
<output name="result" for="a b">60</output>
</form>
https://jsfiddle.net/gxu1rtqL/
The output element can serve as a container element for a calculation or output of a user's action. You can also change the HTML type from number to range and keep the same code and functionality with a different UI element, as shown below.
<form oninput="result.value=parseInt(a.valueAsNumber)+parseInt(b.valueAsNumber)">
<input type="range" id="a" name="a" value="10" /> +
<input type="number" id="b" name="b" value="50" /> =
<output name="result" for="a b">60</output>
</form>
https://jsfiddle.net/gxu1rtqL/2/

You can do a precheck with regular expression wheather they are numbers as like
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
if((x.search(/[^0-9]/g) != -1)&&(y.search(/[^0-9]/g) != -1))
var x = Number(y)+ Number(z);
else
alert("invalid values....");
document.getElementById("demo").innerHTML = x;
}

Use parseFloat it will convert string to number including decimal values.
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = parseFloat(y) + parseFloat(z);
document.getElementById("demo").innerHTML = x;
}
<p>
Click the button to calculate x.
<button onclick="myFunction()">Try it</button>
</p>
<p>
Enter first number:
<input type="text" id="txt1" name="text1" value="1">
Enter second number:
<input type="text" id="txt2" name="text2" value="2">
</p>
<p id="demo"></p>

You can also write :
var z = x - -y ;
And you get correct answer.
<body>
<input type="text" id="number1" name="">
<input type="text" id="number2" name="">
<button type="button" onclick="myFunction()">Submit</button>
<p id="demo"></p>
<script>
function myFunction() {
var x, y ;
x = document.getElementById('number1').value;
y = document.getElementById('number2').value;
var z = x - -y ;
document.getElementById('demo').innerHTML = z;
}
</script>
</body>

Here goes your code by parsing the variables in the function.
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">
<br>Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction() {
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = y + z;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>
Answer

An alternative solution, just sharing :) :
var result=eval(num1)+eval(num2);

Perhaps you could use this function to add numbers:
function calculate(a, b) {
return a + b
}
console.log(calculate(5, 6))

Debug this and help to find the solve this [duplicate]

This question already has answers here:
How do I get the value of text input field using JavaScript?
(16 answers)
Closed 2 years ago.
function stringGen(num) {
var result = "";
var alpha =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
var alpha1 = alpha.length;
for (var i = 0; i < num; i++) {
result += alpha.charAt(Math.floor(Math.random() * alpha1));
}
return result;
}
var number = document.getElementById("num");
console.log(stringGen(number));
<html>
<body>
<div>
Enter the length of character:
<input type="text" id="num" />
<button onclick="stringGen(5)">submit</button>
<p id="result"></p>
</div>
<script type="text/javascript" src="app/index.js"></script>
</body>
</html>
Please find the error. I'm not getting the answer to this. I want to display the random text with the length from the value given in the text field in HTML.

I have update your code to fix not showing random text .
At first i get input data by var num = +document.getElementById("num").value; I use + for convert into integer. you code is not showing becouse you do not write any code to show. use document.getElementById("result").innerHTML =result to show in div.
function stringGen(num) {
var result = "";
var alpha =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
var alpha1 = alpha.length;
for (var i = 0; i < num; i++) {
result += alpha.charAt(Math.floor(Math.random() * alpha1));
}
return result;
}
function showResult(){
var num = +document.getElementById("num").value;
document.getElementById("result").innerHTML =stringGen(num);
}
<div>
Enter the length of character:
<input type="text" id="num" />
<button onclick="showResult()">submit</button>
<p id="result"></p>
</div>

Quantity is connected together not summed up [duplicate]

I am adding two numbers, but I don't get a correct value.
For example, doing 1 + 2 returns 12 and not 3
What am I doing wrong in this code?
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = y + z;
document.getElementById("demo").innerHTML = x;
}
<p>
Click the button to calculate x.
<button onclick="myFunction()">Try it</button>
</p>
<p>
Enter first number:
<input type="text" id="txt1" name="text1" value="1">
Enter second number:
<input type="text" id="txt2" name="text2" value="2">
</p>
<p id="demo"></p>

They are actually strings, not numbers. The easiest way to produce a number from a string is to prepend it with +:
var x = +y + +z;

I just use Number():
var i=2;
var j=3;
var k = Number(i) + Number(j); // 5

You need to use javaScript's parseInt() method to turn the strings back into numbers. Right now they are strings so adding two strings concatenates them, which is why you're getting "12".

Use parseInt(...) but make sure you specify a radix value; otherwise you will run into several bugs (if the string begins with "0", the radix is octal/8 etc.).
var x = parseInt(stringValueX, 10);
var y = parseInt(stringValueY, 10);
alert(x + y);
Hope this helps!

The following may be useful in general terms.
First, HTML form fields are limited to text. That applies especially to text boxes, even if you have taken pains to ensure that the value looks like a number.
Second, JavaScript, for better or worse, has overloaded the + operator with two meanings: it adds numbers, and it concatenates strings. It has a preference for concatenation, so even an expression like 3+'4' will be treated as concatenation.
Third, JavaScript will attempt to change types dynamically if it can, and if it needs to. For example '2'*'3' will change both types to numbers, since you can’t multiply strings. If one of them is incompatible, you will get NaN, Not a Number.
Your problem occurs because the data coming from the form is regarded as a string, and the + will therefore concatenate rather than add.
When reading supposedly numeric data from a form, you should always push it through parseInt() or parseFloat(), depending on whether you want an integer or a decimal.
Note that neither function truly converts a string to a number. Instead, it will parse the string from left to right until it gets to an invalid numeric character or to the end and convert what has been accepted. In the case of parseFloat, that includes one decimal point, but not two.
Anything after the valid number is simply ignored. They both fail if the string doesn’t even start off as a number. Then you will get NaN.
A good general purpose technique for numbers from forms is something like this:
var data=parseInt(form.elements['data'].value); // or parseFloat
If you’re prepared to coalesce an invalid string to 0, you can use:
var data=parseInt(form.elements['data'].value) || 0;

Just add a simple type casting method as the input is taken in text. Use the following:
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = y + z;

This won't sum up the number; instead it will concatenate it:
var x = y + z;
You need to do:
var x = (y)+(z);
You must use parseInt in order to specify the operation on numbers. Example:
var x = parseInt(y) + parseInt(z); [final soulution, as everything us]

Simple
var result = parseInt("1") + parseInt("2");
console.log(result ); // Outputs 3

This code sums both the variables! Put it into your function
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = (y +z);
document.getElementById("demo").innerHTML = x;`

<head>
<script type="text/javascript">
function addition()
{
var a = parseInt(form.input1.value);
var b = parseInt(form.input2.value);
var c = a+b
document.write(c);
}
</script>
</head>
<body>
<form name="form" method="GET">
<input type="text" name="input1" value=20><br>
<input type="text" name="input2" value=10><br>
<input type="button" value="ADD" onclick="addition()">
</form>
</body>
</html>

Or you could simply initialize
var x = 0; ( you should use let x = 0;)
This way it will add not concatenate.

If Nothing works then only try this. This maybe isn't Right way of doing it but it worked for me when all the above failed.
var1 - (- var2)

You are missing the type conversion during the addition step...
var x = y + z; should be var x = parseInt(y) + parseInt(z);
<!DOCTYPE html>
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction()
{
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = parseInt(y) + parseInt(z);
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>

<input type="text" name="num1" id="num1" onkeyup="sum()">
<input type="text" name="num2" id="num2" onkeyup="sum()">
<input type="text" name="num2" id="result">
<script>
function sum()
{
var number1 = document.getElementById('num1').value;
var number2 = document.getElementById('num2').value;
if (number1 == '') {
number1 = 0
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
else if(number2 == '')
{
number2 = 0;
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
else
{
var num3 = parseInt(number1) + parseInt(number2);
document.getElementById('result').value = num3;
}
}
</script>

It's very simple:
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = +y + +z;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>

Try this:
<!DOCTYPE html>
<html>
<body>
<p>Add Section</p>
<label>First Number:</label>
<input id="txt1" type="text"/><br />
<label>Second Number:</label>
<input id="txt2" type="text"/><br />
<input type="button" name="Add" value="Add" onclick="addTwoNumber()"/>
<p id="demo"></p>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = Date();
}
function addTwoNumber(){
var a = document.getElementById("txt1").value;
var b = document.getElementById("txt2").value;
var x = Number(a) + Number(b);
document.getElementById("demo").innerHTML = "Add Value: " + x;
}
</script>
</body>
</html>

If we have two input fields then get the values from input fields, and then add them using JavaScript.
$('input[name="yourname"]').keyup(function(event) {
/* Act on the event */
var value1 = $(this).val();
var value2 = $('input[name="secondName"]').val();
var roundofa = +value2+ +value1;
$('input[name="total"]').val(addition);
});

This can also be achieved with a more native HTML solution by using the output element.
<form oninput="result.value=parseInt(a.valueAsNumber)+parseInt(b.valueAsNumber)">
<input type="number" id="a" name="a" value="10" /> +
<input type="number" id="b" name="b" value="50" /> =
<output name="result" for="a b">60</output>
</form>
https://jsfiddle.net/gxu1rtqL/
The output element can serve as a container element for a calculation or output of a user's action. You can also change the HTML type from number to range and keep the same code and functionality with a different UI element, as shown below.
<form oninput="result.value=parseInt(a.valueAsNumber)+parseInt(b.valueAsNumber)">
<input type="range" id="a" name="a" value="10" /> +
<input type="number" id="b" name="b" value="50" /> =
<output name="result" for="a b">60</output>
</form>
https://jsfiddle.net/gxu1rtqL/2/

You can do a precheck with regular expression wheather they are numbers as like
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
if((x.search(/[^0-9]/g) != -1)&&(y.search(/[^0-9]/g) != -1))
var x = Number(y)+ Number(z);
else
alert("invalid values....");
document.getElementById("demo").innerHTML = x;
}

Use parseFloat it will convert string to number including decimal values.
function myFunction() {
var y = document.getElementById("txt1").value;
var z = document.getElementById("txt2").value;
var x = parseFloat(y) + parseFloat(z);
document.getElementById("demo").innerHTML = x;
}
<p>
Click the button to calculate x.
<button onclick="myFunction()">Try it</button>
</p>
<p>
Enter first number:
<input type="text" id="txt1" name="text1" value="1">
Enter second number:
<input type="text" id="txt2" name="text2" value="2">
</p>
<p id="demo"></p>

You can also write :
var z = x - -y ;
And you get correct answer.
<body>
<input type="text" id="number1" name="">
<input type="text" id="number2" name="">
<button type="button" onclick="myFunction()">Submit</button>
<p id="demo"></p>
<script>
function myFunction() {
var x, y ;
x = document.getElementById('number1').value;
y = document.getElementById('number2').value;
var z = x - -y ;
document.getElementById('demo').innerHTML = z;
}
</script>
</body>

Here goes your code by parsing the variables in the function.
<html>
<body>
<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>
<br/>
<br/>Enter first number:
<input type="text" id="txt1" name="text1">
<br>Enter second number:
<input type="text" id="txt2" name="text2">
<p id="demo"></p>
<script>
function myFunction() {
var y = parseInt(document.getElementById("txt1").value);
var z = parseInt(document.getElementById("txt2").value);
var x = y + z;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>
Answer

An alternative solution, just sharing :) :
var result=eval(num1)+eval(num2);

Perhaps you could use this function to add numbers:
function calculate(a, b) {
return a + b
}
console.log(calculate(5, 6))

How can i do a simple switch of characters from using indexes

Greetings I am trying to do a simple swap by comparing 2 numbers from a string and the switching the higher number to the left. I am using a while loop to make the changes but i get a TypeError: input is not a function chartest.html:32:4
I do not see what i am doing wrong can anyone look at my code. Here is a look at my code.
<body>
<form>
Enter numbers to be sorted from into high to low
<input id="num" type="text" value="" >
<br>output<input id="forTest" type="text">
<br><button type="button" onclick="calc(); return false" >Enter</button>
<input type="reset">
</form>
<p id="what"></p>
<script>
function calc()
{
var input = document.getElementById("num").value;
var wordlength = input.length;
var i = 0;
while(i < wordlength -1)
{
a = input.charAt(i);
b = input.charAt(i+1);
if(a < b)
{
input(i) = b;
input(i+1) =a;
}
i++;
}
alert(input);
//document.getElementById("forTest").value = testString;
//document.getElementById("what").innerHTML = testString;
}
</script>
</body>

Functional programming is your friend :)
var input = document.getElementById("num").value;
var arrayOfChars=input.split(""); //Or split by comma or whatever
var sortedArrayOfChars=arrayOfChars.sort(sortingFunction);
function sortingFunction(a,b){return a-b;}
Or, as a 1 liner...
input.split("").sort(function(a,b){return a-b;})

Develop Reference

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