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

  while (i < tokensLength) {
    if (l = checkInterpolation(i) || checkNumber(i)) i += l;
    else break;
  }

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

  while (i < tokensLength) {
    if (l = checkInterpolation(i) || checkNumber(i)) i += l;
    else break;
  }

  return i - start;
}
function checkNumberOrInterpolation ( i ) { const start = i ; let l ; while ( i < tokensLength ) { if ( l = checkInterpolation ( i ) || checkNumber ( i ) ) i += l ; else break ; } return i - start ; }
Check if token is a number or an interpolation
@param {number} i Token's index number
@return {number}
Check if token is a number or an interpolation