const libs =
  `des_system_lib   std synopsys std_cell_lib des_system_lib dw02 dw01 ramlib ieee
  dw01             ieee dw01 dware gtech
  dw02             ieee dw02 dware
  dw03             std synopsys dware dw03 dw02 dw01 ieee gtech
  dw04             dw04 ieee dw01 dware gtech
  dw05             dw05 ieee dware
  dw06             dw06 ieee dware
  dw07             ieee dware
  dware            ieee dware
  gtech            ieee gtech
  ramlib           std ieee
  std_cell_lib     ieee std_cell_lib
  synopsys`;

// A map of the input data, with the keys as the packages, and the values as
// and array of packages on which it depends.
const D = libs
  .split('\n')
  .map(e => e.split(' ').filter(e => e != ''))
  .reduce((p, c) =>
    p.set(c[0], c.filter((e, i) => i > 0 && e !== c[0] ? e : null)), new Map());
[].concat(...D.values()).forEach(e => {
  D.set(e, D.get(e) || [])
});

// The above map rotated so that it represents a DAG of the form
// Map {
//    A => [ A, B, C],
//    B => [C],
//    C => []
// }
// where each key represents a node, and the array contains the edges.
const G = [...D.keys()].reduce((p, c) =>
  p.set(
    c,
    [...D.keys()].filter(e => D.get(e).includes(c))),
  new Map()
);

// An array of leaf nodes; nodes with 0 in degrees.
const Q = [...D.keys()].filter(e => D.get(e).length == 0);

// The result array.
const S = [];
while (Q.length) {
  const u = Q.pop();
  S.push(u);
  G.get(u).forEach(v => {
    D.set(v, D.get(v).filter(e => e !== u));
    if (D.get(v).length == 0) {
      Q.push(v);
    }
  });
}

console.log('Solution:', S);