Is there a bignum library for JavaScript or built-in that I can include like
<script type="text/javascript" src="the_bignum_library.js"></script>
?
I think my users would prefer to enter numbers in a web page and wait 7 seconds for a result, rather than download an executable and click through a bunch of "this executable could possibly harm your computer" warning screens to install it.
I've considered basing my own off of http://github.com/silentmatt/javascript-biginteger or http://www.mainebrook.com/john/fun/euler.html. Or would you recommend calling from JavaScript into a Java bignum library such as apfloat?
Update(2019-08-19): BigInt is now part of Firefox and Chrome; you no longer need a library:
const bigInt1 = 1111111111111111111111111111111n;
const bigInt2 = BigInt("1111111111111111111111111111111")
console.log((bigInt1 + bigInt2)+"")
Original answer:
If you need arbitrary-precision decimal numbers, use Javascript-bignum, as it is correct and fast.