Current Events > Programmers. I'm making a calculator with Javascript and I'm getting an error

(+) Yeah! (+)

function calculator() {
var val1 = theForm.txtval1.value;
var val2 = theForm.txtval2.value;
var math = document.getElementById("math").value;
theForm.Total.value = math;

if (math == "add") {
document.getElementById("Tol").value = val1 + val2;
}

if (math == "minus") {
document.getElementById("Tol").value = val1 - val2;
}

if (math == "times") {
document.getElementById("Tol").value = val1 * val2;
}

if (math == "divide") {
document.getElementById("Tol").value = val1 / val2;
}
}

When I use it, the subtraction, times, division are correct, but the sum always combines the numbers I entered together.
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Well if it wasn't JavaScript I'd say check your data types.
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uh
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<form name="theForm" id="frmcalculator" method="get">
<h1>Simple Calculator</h1>

Value 1: <input type="text" id="val1" name="txtval1"><br><br>
<select id="math">
<option value="add">+</option>
<option value="minus">-</option>
<option value="times">*</option>
<option value="divide">/</option>
</select><br><br>
Value 2: <input type="text" id="val2" name="txtval2"><br>

<hr>

Total: <input type="text" id="Tol" name="Total"><br><br>

Here is my HTML
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EThe + operator is overloaded in Javascript.
It adds, or if the datatypes are string, it concatenates.

"Hello " + "world" = "Hello world".
"3" + "2" = "32".

Since you're taking the values from a text box, by default the values are strings. Javascript does have datatypes--it just doesn't support variable typing. So what you need to do is cast your values to integers before adding. I don't remember the cast function name but just google "javascript cast int" and you should find it.
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have you tried not doing any of that
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DevsBro posted...

EThe + operator is overloaded in Javascript.
It adds, or if the datatypes are string, it concatenates.

"Hello " + "world" = "Hello world".
"3" + "2" = "32".

Since you're taking the values from a text box, by default the values are strings. Javascript does have datatypes--it just doesn't support variable typing. So what you need to do is cast your values to integers before adding. I don't remember the cast function name but just google "javascript cast int" and you should find it.

parseInt. So I use that to add everything.
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Should work. parseInt("1") + parseInt("2") should give you 3.
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This is one beef I have with lots of languages. Using + for concatenation gives you all kinds of simple caveats you can fall into. It's most noticeable in a language lke Javascript but even strongly-typed languages like Java will throw you off if you're still learning or in a hurry or whatever.

System.out.println("The number is " + 3 + 2) doesn't do what you might think.

I prefer the way you see it in Ada and VB, where the conctenate operator is & instead. No chance of those kinds of bugs.
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It worked. Thanks dude.
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DevsBro posted...

Javascript does have datatypes--it just doesn't support variable typing

There is something deeply wrong with people who design languages like this

Rexdragon125 posted...

DevsBro posted...

Javascript does have datatypes--it just doesn't support variable typing

There is something deeply wrong with people who design languages like this

*shrugs*
It generally works pretty well. But like anything, it has its quirks that you have to work around on occasion.
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