The adding up button doesn't work in javascript

Question

I made a simple calculator in javascript but the + button doesn't work and it just show the numbers near together

Here is my code:

<script>
function calc(operator) {
    var x = document.getElementById("inp1").value;
    var y = document.getElementById("inp2").value;
    var z = 0;

    switch (operator) {
        case "+":
        z = x + y;
        break;
        case "-":
        z = x - y;
        break;
        case "*":
        z = x * y;
        break;
        case "/":
        z = x / y;
        break;
    }
    document.getElementById("result").innerHTML=z;
}
</script>

The values you read at the start are strings. to get numbers, use `parseInt()` or `parseFloat()`. — Sirko, Sep 02 '14 at 07:11
possible duplicate of [how to sum two numbers from input tag?](http://stackoverflow.com/questions/11961474/how-to-sum-two-numbers-from-input-tag) — Viktor Bahtev, Sep 02 '14 at 07:11
possible duplicate of [How to add two strings as if they were numbers?](http://stackoverflow.com/questions/8976627/how-to-add-two-strings-as-if-they-were-numbers) — dcorking, Sep 02 '14 at 07:23
@MelodyHajian you wrote "i didn't even know what is the problem." Don't worry, the 'duplicate' flag is not a criticism of your question. Instead, the link from your question to the canonical question allows users to answers that apply to both questions. — dcorking, Sep 02 '14 at 08:23
Drat - I can't edit my comment. I meant to write: "allows users to _find_ answers that apply to both questions" — dcorking, Sep 02 '14 at 08:53

score 2 · Accepted Answer · answered Sep 02 '14 at 07:10

2

You may use like this:

z= +x + +y; // + is prefixed to convert input into number

answered Sep 02 '14 at 07:10

Bhojendra Rauniyar

83,432
35
168
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score 2 · Answer 2 · answered Sep 02 '14 at 07:13

The x and y variables contain strings. Parse them to numbers:

var x = parseFloat(document.getElementById("inp1").value);
var y = parseFloat(document.getElementById("inp2").value);

It happens to work for the other operators, because there are no subtraction, multiplication or division for strings, it figures out that it has to convert the strings to numbers.

score 1 · Answer 3 · answered Sep 02 '14 at 07:23

var x=document.getElementById("inp1").value;
var y=document.getElementById("inp2").value;

return you values in those text boxes as strings.

When you use + operator on strings, it will concatenate the values. If you use the same operator on numbers, it will add the values.

You will need to parse the text box values into integer using the parseInt function using one of the following ways.

var x=parseInt(document.getElementById("inp1").value);
var y=parseInt(document.getElementById("inp2").value);

and then do z=x+y; I would recommend this because all the operations, not just addition, will be perfomed on the integers.

or simply change z=z+y; to look like z = parseInt(x) + parseInt(y);

score 1 · Answer 4 · answered Sep 02 '14 at 07:25

1

A quick way to convert a string to a number is to use the unary + operator.

z = +x + +y

or

z = parseInt(x) + parseInt(y);

answered Sep 02 '14 at 07:25

Rahul K

413
3
11

score 1 · Answer 5 · answered Sep 02 '14 at 07:31

1

var x = parseInt(document.getElementById("inp1").value);

this converts your "string" number to integer, also you can use parseFloat() if you have float numbers

answered Sep 02 '14 at 07:31

CMS

704
3
9
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score 1 · Answer 6 · answered Sep 02 '14 at 07:47

1

You may use like this:

var x = document.getElementById("inp1").value*1;
var y = document.getElementById("inp2").value*1;

x in this moment is number!!

More clean for me!!!

answered Sep 02 '14 at 07:47

Seconddj

9
2

1

This is the only answer with `*1`. What does it do? (I guess it multiplies the string by 1 and so converts it to an integer.) Since you recommend this approach (and I agree that it looks nice), I suggest you post it as an answer to the canonical question http://stackoverflow.com/questions/8976627/how-to-add-two-strings-as-if-they-were-numbers – dcorking Sep 02 '14 at 08:17
1

when multiplied by 1 (* 1), is converted into a number, not an integer, it is different. – Seconddj Sep 17 '14 at 07:57

The adding up button doesn't work in javascript

6 Answers6