CODEWITHSUNDEEP
javascriptmathvariables
codedude
codedude

Reputation: 6519

Adding Javascript variables

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?

Upvotes: 1

Views: 26759

Answers (5)

Zack
Zack

Reputation: 492

Mine worked well with parsing them to Float as I am having decimal digits. Instead of parseInt(), I used parseFloat().

I hope it'll help somebody in future.

Upvotes: 0

Damen TheSifter
Damen TheSifter

Reputation: 911

parseInt is your firend here..

function math (form) {
  var input1 = form.input1.value;
  var input2 = form.input2.value;
  var input3 = parseInt(input1, 10) + parseInt(input2, 10);
  document.write (input3);
}

Upvotes: 3

Andrew
Andrew

Reputation: 13853

They are strings when you read them in, they must be parsed first,

var input3 = parseInt(input1, 10) + parseInt(input2, 10);

[Edit] Just to elaborate, the difference between parseInt and the Unary Plus is in the error handling,

var a = parseInt('123o45', 10); //123
var b = +'123o45' // NaN

Upvotes: 12

Christofer Eliasson
Christofer Eliasson

Reputation: 33865

You would have to parse them to integers first using parseInt.

Upvotes: 1

pimvdb
pimvdb

Reputation: 154838

.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.

Upvotes: 17

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