Helo!
I wrote this:
<!DOCTYPE html>
<html>
<body>
<p>Click the button to demonstrate the prompt box.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x;
var number=prompt("nb","nbpl?");
if (number!=0)
{
x=number+2;
document.getElementById("demo").innerHTML=x;
}
}
</script>
</body>
</html>
It works with: number/2, number*2, number-2, but just not with number+2.
Please, any hints how to solve the problem?
Many thanks!
The problem arises from the dual nature of the + operator used for both numeric addition and string concatenation. If both operands are numbers to start with will the + operator performs addition otherwise it converts all of its operands to strings and does concatenation.
Therefore 2 + 2 = 22
Convert the string to a number with parseInt (for integers) or ParseFloat (for floating point numbers).
e.g.
x=parseInt(number)+2;
More info here and [URL=“http://www.javascripter.net/faq/convert2.htm”]here.
In addition to what Paul says, note that the parseInt function takes an optional second parameter (radix) that specifies which numeral system is to be used.
For example, a radix of 16 (hexadecimal) indicates that the number in the string should be parsed from a hexadecimal number to a decimal number.
If the radix parameter is omitted, JavaScript assumes the following:
If the string begins with “0x”, the radix is 16 (hexadecimal)
If the string begins with “0”, the radix is 8 (octal). This feature is deprecated
If the string begins with any other value, the radix is 10 (decimal)[/QUOTE]
If your string is already in the form of a number, it might be better to use Number() which converts the object argument to a number that represents the object’s value.
If the value cannot be converted to a legal number, NaN is returned.
An interesting shorthand for this is the unary plus: http://niki4810.github.io/blog/2013/08/20/unary-plus-operator-shorthand-for-converting-string-to-number-in-javascript/
The correct JavaScript function for converting a string to a number is
num = Number(str)
or you can use the short version
num = (+str)
note that to use the short version you must wrap the parentheses around the + and the string so that it operates as a unary + - which always converts to a number).
Hello!!!
Please, how to get each result in other line? LIke:
10
2
p.s. I tried with \ and with <br> but no result…
Code is here:
<!DOCTYPE html>
<html>
<body>
<p>Click the button to demonstrate the prompt box.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x;
var nr=prompt("Please enter number","number1");
var nr2=prompt("Please enter number","number2");
x=parseInt(nr)+parseInt(nr2)+nr-nr2;
document.getElementById("demo").innerHTML=x;
}
</script>
</body>
</html>