function parseRangeHeader()

in workbox-v4.3.1/workbox-range-requests.dev.js [83:121]
30 lines of code
8 McCabe index (conditional complexity)

  function parseRangeHeader(rangeHeader) {
    {
      assert_mjs.assert.isType(rangeHeader, 'string', {
        moduleName: 'workbox-range-requests',
        funcName: 'parseRangeHeader',
        paramName: 'rangeHeader'
      });
    }

    const normalizedRangeHeader = rangeHeader.trim().toLowerCase();

    if (!normalizedRangeHeader.startsWith('bytes=')) {
      throw new WorkboxError_mjs.WorkboxError('unit-must-be-bytes', {
        normalizedRangeHeader
      });
    } // Specifying multiple ranges separate by commas is valid syntax, but this
    // library only attempts to handle a single, contiguous sequence of bytes.
    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Range#Syntax


    if (normalizedRangeHeader.includes(',')) {
      throw new WorkboxError_mjs.WorkboxError('single-range-only', {
        normalizedRangeHeader
      });
    }

    const rangeParts = /(\d*)-(\d*)/.exec(normalizedRangeHeader); // We need either at least one of the start or end values.

    if (rangeParts === null || !(rangeParts[1] || rangeParts[2])) {
      throw new WorkboxError_mjs.WorkboxError('invalid-range-values', {
        normalizedRangeHeader
      });
    }

    return {
      start: rangeParts[1] === '' ? null : Number(rangeParts[1]),
      end: rangeParts[2] === '' ? null : Number(rangeParts[2])
    };
  }