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I can't figure out the reason 100000000000000030/10 = 10000000000000004 in JavaScript, I haven't seen this problem in other questions.

  <script>
    alert(100000000000000030/10);
  </script>

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    Just curious: in which context are you using this calculation? Because that's a really big number. Can you show us the code around it please? Commented Dec 14, 2018 at 19:44
  • 1
    "Computer math is to math what computer music is to music." Maybe write some code that demonstrates this question. Without a minimal reproducible example this question isn't complete. Commented Dec 14, 2018 at 19:44
  • 3
    Javascript uses double-precision floating point for numbers. You're bound to encounter some anomalies like this. Commented Dec 14, 2018 at 19:44
  • There are JS math libraries out there which remove most of the inaccuracies and limits (e.g max number). I wouldn't recommend to use vanilla JS for math that requires absolute precision. Commented Dec 14, 2018 at 19:48
  • You also get the wrong result for 100000000000000030 + 1 or 100000000000000030 - 1. Or try 100000000000000030 + 9 for more fun. Commented Dec 14, 2018 at 19:48

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Before doing this calculation you may want to know that whether this number is a safe javascript number or not. you can use - Number.isSafeInteger(100000000000000030), to know that.

"The MAX_SAFE_INTEGER constant has a value of 9007199254740991 (9,007,199,254,740,991 or ~9 quadrillion). The reasoning behind that number is that JavaScript uses double-precision floating-point format numbers as specified in IEEE 754 and can only safely represent numbers between -(253 - 1) and 253 - 1."

You may also want to read more here - Division and remainder of large numbers in JavaScript

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