Listified Tokens, or Somebody's JavaScript Homework

const listified = `(1, 2, 3), (4, 5, 6), (7, 8, 9), (5, junk, 100, 2eggs)`    .match(/\((.*?)\)/g)  .reduce(    (a, c) => [      ...a,      [        ...c          .match(/([0-9]+)(?=[ ,\)])/g)          .map((el) => !isNaN(el) && parseInt(el)),      ],    ],    []  );console.log(listified);

// Convert strings of the form `"(1, 2, 3), (4, 5, 6), (7, 8, 9)"` into// multidimensional arrays of the form `[[1, 2, 3], [4, 5, 6], [7,8,9]]`.const listifiedTokens = (str) => {  let data = [];  let ws = [];  let x;  for (c of str) {    // Taking pains to prevent type-coercsion.    if (!isNaN(c)) {      x = x ? `${x}${c}` : c;    }    // Start a new work set and overwrite    // any existing work set.    if (c === "(") {      ws = [];    }    // ')' and ',' terminate a list entry,    // and x must be a number before we parse.    if ([")", ","].includes(c) && !isNaN(x)) {      ws = [...ws, parseInt(x, 10)];    }    // Report the work set.    if (c === ")") {      data = [...data, ws];    }    // Whenever c is NaN, we flush x    // because this only happens at the end    // of a valid list or when the list item    // contains an unsupported value.    if (isNaN(c)) {      x = undefined;    }  }  return data;};const str = `(1, 2, 3), (4, 5, 6), (7, 8, 8, 9), (100, 2egg, 5, bananas)`;console.log(listifiedTokens(str));