Generate, and decode, base64 VLQ mappings for source maps and other uses
npm install vlqConvert integers to a Base64-encoded VLQ string, and vice versa. No dependencies, works in node.js or browsers, supports AMD.
Sourcemaps are the most likely use case. Mappings from original source to generated content are encoded as a sequence of VLQ strings.
A variable-length quantity is a compact way of encoding large integers in text (i.e. in situations where you can't transmit raw binary data). An integer represented as digits will always take up more space than the equivalent VLQ representation:
| Integer | VLQ |
| :------------------ | :--------- |
| 0 | A |
| 1 | C |
| -1 | D |
| 123 | 2H |
| 123456789 | qxmvrH |
``bash`
npm install vlq
vlq.encode accepts an integer, or an array of integers, and returns a string:
`js`
vlq.encode(123); // '2H';
vlq.encode([123, 456, 789]); // '2HwcqxB'
vlq.decode accepts a string and always returns an array:
`js``
vlq.decode('2H'); // [123]
vlq.decode('2HwcqxB'); // [123, 456, 789]
Since JavaScript bitwise operators work on 32 bit integers, the maximum value this library can handle is 2^30 - 1, or 1073741823.
See here for an example of using vlq.js with sourcemaps.
Adapted from murzwin.com/base64vlq.html by Alexander Pavlov.
MIT.