list.sort(orderBy(["first", "second", "…", "penultimate", "last"])

sortOrderBy.js

// Allows user to list some (but not all) items to be sorted in the specified order.
// If the ellipsis character … (option-; on Mac) is present, can specify order of things to go after everything else.

const debug = false ? console.log : ()=>{}

console.log(["!","o","r","s","d","e","t"].sort(orderBy(["s","o","…","e","d","!"]))) // s o r t e d !
console.log(["b","c","a"].sort(orderBy(["c"]))) // c b a

function orderBy (ordering) { return (a, b) => { // columns specified in orderOfColumns come first, then other columns
  const rest_index = ordering.indexOf("…") === -1 ? Infinity : ordering.indexOf("…")
  const a_index = ordering.indexOf(a)
  const b_index = ordering.indexOf(b)
  const A_ORDERED = a_index + 1
  const B_ORDERED = b_index + 1
  const A_FIRST = A_ORDERED && a_index < rest_index
  const B_FIRST = B_ORDERED && b_index < rest_index
  const A_LAST = A_ORDERED && a_index > rest_index
  const B_LAST = B_ORDERED && b_index > rest_index
  const SORT_NORMALLY = a - b
  const SORT_BY_ORDER = a_index - b_index
  const SORT_A_BEFORE_B = -1
  const SORT_B_BEFORE_A = 1
  if (A_ORDERED && B_ORDERED) {
    if (A_FIRST && B_FIRST) { debug(`${a} A_FIRST, ${b} B_FIRST -> SORT_BY_ORDER`); return SORT_BY_ORDER }
    if (A_FIRST && B_LAST) { debug(`${a} A_FIRST, ${b} B_LAST -> A_BEFORE_B`); return SORT_A_BEFORE_B }
    if (A_LAST && B_FIRST) { debug(`${a} A_LAST, ${b} B_FIRST -> B_BEFORE_A`); return SORT_B_BEFORE_A }
    if (A_LAST && B_LAST) { debug(`${a} A_LAST, ${b} B_LAST -> SORT_BY_ORDER`); return SORT_BY_ORDER }
    throw (`Impossible ordering ${a} ${b} ${ordering}`)
  }
  if (A_FIRST) { debug(`${a} A_FIRST, ${b} B_UNORDERED -> A_BEFORE_B`); return SORT_A_BEFORE_B }
  if (A_LAST) { debug(`${a} A_LAST, ${b} B_UNORDERED -> B_BEFORE_A`); return SORT_B_BEFORE_A }
  if (B_FIRST) { debug(`${a} A_UNORDERED, ${b} B_FIRST -> B_BEFORE_A`); return SORT_B_BEFORE_A }
  if (B_LAST) { debug(`${a} A_UNORDERED, ${b} B_LAST -> A_BEFORE_B`); return SORT_A_BEFORE_B }
  debug(`${a} A_UNORDERED ${b} B_UNORDERED -> SORT_NORMALLY`)
  return SORT_NORMALLY
} }