Question

So, I’m relatively new to JavaScript and I was wondering how I would add the values from two inputs and echo out the result. Here’s what I have so far:

function math (form) {
    var input1 = form.input1.value;
    var input2 = form.input2.value;
    var input3 = input1 + input2;
    document.write (input3);
}

<form action="" method="GET">
   <input type="text" name="input1">
   <input type="text" name="input2">
   <input type="button" name="button" onClick="math(this.form)">
</form> 

I expected that when I entered a number into each input it would spit out the sum of the two numbers. Instead it just prints both numbers individually.

How can I get it to print the sum of the two numbers?

Answer 1

.value gives the characters in the textbox, i.e. a string. You somehow need to tell JavaScript that it’s a number. Otherwise you’re concatenating the strings (str + str is concatenating; num + num is adding arithmetically).

String to number conversion is most easily done with + like this:

+input1

So in your case:

document.write(+input1 + +input2);

However, document.write is not the way to display things. You probably want alert, or put it in another textbox or something like that. document.write will clear the screen.