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Adding two numbers with decimals

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Jun 26.2003

Hi, looking for some help here. All I am trying to do is add two numbers. 138.9 + 27.33 and instead of 166.23 i get 166.2300000000002. Can anyone tell me why? Here is my code

function button1_onclick() {
var TallyAmt = 0;
ThisAmt = document.form1.text1.value;
TallyAmt = (TallyAmt + (ThisAmt * 1));
alert (TallyAmt);
ThisAmt = document.form1.text2.value;
TallyAmt = (TallyAmt + (ThisAmt * 1));
alert (TallyAmt);
ThisAmt = document.form1.text3.value;
TallyAmt = (TallyAmt + (ThisAmt * 1));
alert (TallyAmt);
}
Thanks a bunch

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JavaScript

8 Comments(s) ↴

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@pyroJun 26.2003 — Use [URL=http://devedge.netscape.com/library/manuals/2000/javascript/1.5/reference/number.html#1200964]toFixed()[/URL] to return it to a certain number of decimal places.
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@David_HarrisonJun 26.2003 — Computers are crap with decimals so I've found that this would be the best way to add two variables a and b:

var n=0;

var o=0;

while(Math.round(a*Math.pow(10,n))!=(a*Math.pow(10,n))){n++;}

while(Math.round(b*Math.pow(10,o))!=(b*Math.pow(10,o))){o++;}

var p=(n>=o)?n : o ; // Had to leave spaces here because : o turns into :o

a=a*Math.pow(10,p);

b=b*Math.pow(10,p);

answer=(a+b)/Math.pow(10,p);

It's a bit long winded but it's more accurate.
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@pyroJun 27.2003 — What's wrong with toFixed()?
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@David_HarrisonJun 27.2003 — That will only work to return a specified amount of decimal places whereas mine will return the actual number of decimal numbers (up to about 20 anyway).
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@pyroJun 27.2003 — 138.9 + 27.33 should only return two decimals.
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@David_HarrisonJun 27.2003 — Yes, but if he used toFixed() and set it to return two decimal places, what if he wanted to add 23.8306 and 478.2669, they both have four decimal places.
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@pyroJun 27.2003 — [i]Originally posted by lavalamp [/i]

[B]Yes, but if he used toFixed() and set it to return two decimal places, what if he wanted to add 23.8306 and 478.2669, they both have four decimal places. [/B][/QUOTE]Umm... He would set it to return four decimal places...
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@David_HarrisonJun 27.2003 — What if he didn't know how many dp's the numbers were going to be to?
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