From: FAQ server on 27 May 2010 19:00 ----------------------------------------------------------------------- FAQ Topic - Why does simple decimal arithmetic give strange results? ----------------------------------------------------------------------- For example, ` 5 * 1.015 ` does not give exactly ` 5.075 ` and ` 0.06+0.01 ` does not give exactly ` 0.07 ` in javascript. ECMAScript numbers are represented in binary as IEEE-754 (IEC 559) Doubles, with a resolution of 53 bits, giving an accuracy of 15-16 decimal digits; integers up to just over ` 9e15 ` are precise, but few decimal fractions are. Given this, arithmetic is as exact as possible, but no more. Operations on integers are exact if the true result and all intermediates are integers within that range. In particular, non-integer results should not normally be compared for equality; and non-integer computed results commonly need rounding; see http://jibbering.com/faq/#formatNumber http://msdn.microsoft.com/en-us/library/7wkd9z69%28VS.85%29.aspx http://www.merlyn.demon.co.uk/js-misc0.htm#DW4 Otherwise, use ` Math.round ` on the results of expressions which should be of integer value. The complete comp.lang.javascript FAQ is at http://jibbering.com/faq/ -- The sendings of these daily posts are proficiently hosted by http://www.pair.com.
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