If a smaller and simpler library is required see big.js. It's less than half the size but only works with decimal numbers and only has half the methods. It also has fewer configuration options than ...

Takes a UTF-8 encoded string and a codepoint index. Calculates the codepoint at that index. Then, calculates the code point with value one higher (so e.g. for ”é“ U+00E9 that would be “ê” (U+00EA), ...