import RangeParser = require('range-parser'); declare var console: { assert(b: boolean): void }; console.assert(RangeParser(200, `malformed`) === -2); console.assert(RangeParser(200, `bytes=500-20`) === -1); const range = RangeParser(1000, `bytes=0-499`); if (typeof range !== 'number') { console.assert(range.type === `bytes`); console.assert(range.length === 1); }