src/sass/parse.js
function checkCustomProperty(i) {
  const start = i;
  let l;

  if (i >= tokensLength) return 0;

  if (tokens[i].type !== TokenType.HyphenMinus ||
      tokens[i + 1] && tokens[i + 1].type !== TokenType.HyphenMinus) return 0;

  // Skip `--`
  i += 2;

  if (l = checkIdentOrInterpolation(i)) i += l;
  else return 0;

  return i - start;
}
function checkCustomProperty(i) {
  const start = i;
  let l;

  if (i >= tokensLength) return 0;

  if (tokens[i].type !== TokenType.HyphenMinus ||
      tokens[i + 1] && tokens[i + 1].type !== TokenType.HyphenMinus) return 0;

  // Skip `--`
  i += 2;

  if (l = checkIdentOrInterpolation(i)) i += l;
  else return 0;

  return i - start;
}
function checkCustomProperty ( i ) { const start = i ; let l ; if ( i >= tokensLength ) return 0 ; if ( tokens [ i ] . type !== TokenType . HyphenMinus || tokens [ i + 1 ] && tokens [ i + 1 ] . type !== TokenType . HyphenMinus ) return 0 ; // Skip `--` i += 2 ; if ( l = checkIdentOrInterpolation ( i ) ) i += l ; else return 0 ; return i - start ; }
Check if token is part of a custom property
@param {Number} i Token's index number
@return {Number} Length of the property
Check if token is part of a custom property