Addition and Subtraction with Negative Numbers

Question

I tried adding and subtracting negative numbers with this code

var num1 = parseInt(document.form1.num1.value);
var num2 = parseInt(document.form1.num2.value);
if(operand == "plus"){
    var sum = parseInt(num1+num2);
    // add alerts to check
    alert (num1);
    alert (num2);
    alert (sum);
}else{
    var sum = parseInt(num1-num2);
}

but when I print the result (sum), the program ignore the negative number and just count it as if it's a positive number. I tried delete the parseInt but nothing changes. for those who's confused : my inputs are num1 and num2. using the code I had, if I input (4) and (-2) and choose plus sign, sum = 6. they dont count the negative as negative, but as positive.

update : apparently even if I input (-2), they save it as (2).

parseInt(num1) - parseInt(num2) wont work if I have 2 negative numbers. — Hikmah Az, Dec 21 '14 at 13:51
@jack , if I choose plus sign, and input 4 and 5, the sum will be 9. and if I choose minus and input 6 and 2, the sum is 4. there's nothing wrong with the branch. — Hikmah Az, Dec 21 '14 at 14:00
Well, `parseInt("4" + "-2")` gives `4` and `parseInt(4-2)` gives `2`; but definitely not `6` ... — Ja͢ck, Dec 21 '14 at 14:04
Do you realise that if you subtract a negative number it gives the same result as adding the same number's absolute value? Example: `-4 - -9 = 5 = -4 + 9`. — 11684, Dec 21 '14 at 14:13
@HikmahAz What code? You've shared a snippet that I've put into a working example; it's your task to either find out the differences or share more code. — Ja͢ck, Dec 21 '14 at 14:23
I'm really sorry, it was my own fault. I put the order of codes wrong. thanks everyone who offered help. — Hikmah Az, May 08 '15 at 03:16

wvdz · Answer 1 · 2014-12-21T14:26:50.190

1

Assuming sum1 and sum2 are string literals, what you should do is parseInt(num1) + parseInt(num2)

It seems your problem is that you're applying a double negative, which makes a positive:

4 - -2 == 4 + 2

edited Dec 21 '14 at 14:26

answered Dec 21 '14 at 13:44

wvdz

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Addition and Subtraction with Negative Numbers

1 Answers1