validate brackets and merge sorted arrays.

index.js

(function() {
  // 1

  function smartJoin(arrA, arrB) {
    let aIndex = 0;
    let bIndex = 0;
    const result = [];

    while (aIndex < arrA.length || bIndex < arrB.length) {
      const itemA = arrA[aIndex];
      const itemB = arrB[bIndex];

      if (
        itemA < itemB
        || (bIndex >= arrB.length && aIndex < arrA.length)
      ) {
        result.push(itemA);
        aIndex++;
        continue;
      }
      if (
        itemA >= itemB
        || (aIndex >= arrA.length && bIndex < arrB.length)
      ) {
        result.push(itemB);
        bIndex++;
        continue;
      }
      console.error("Something go wrong...");
      break;
    }
    return result;
  }

  const a = [4, 6, 10, 15];
  const b = [1, 5, 7, 12, 20];
  console.log(smartJoin(a, b));
  const a1 = [30, 31, 100];
  const b1 = [1, 3, 4, 5, 6, 7, 8, 9];
  console.log(smartJoin(a1, b1));
  const a2 = [1, 3, 4, 5, 6];
  const b2 = [20, 30, 40, 50, 60, 90, 100];
  console.log(smartJoin(a2, b2));
  const a3 = [1, 3, NaN];
  const b3 = [2, 4, 5];
  console.log(smartJoin(a3, b3));
})();

(function() {
  // 2
  function validate(str) {
    const arrStr = str.split("");
    const validSymbols = {
      "(": ")",
      "{": "}",
      "[": "]",
    };
    let stack = [];

    arrStr.forEach((letter) => {
      if (["(", "{", "[", "]", "}", ")"].includes(letter)) {
        if (["(", "{", "["].includes(letter)) {
          stack.push(letter);
        } else {
          const last = stack.pop();
          if (validSymbols[last] !== letter) {
            throw new Error("invalid: " + str);
          }
        }
      }
    });
    if (stack.length !== 0) {
      throw new Error("!invalid: " + str);
    }
    return `valid: ${str}`
  }

  console.log(validate("()"));
  console.log(validate("ab(cd()ef)g"));
  console.log(validate("[{()}]"));

  try {
    validate(")(");
  } catch (e) {
    console.log(e.message);
  }
  try {
    validate("a)b(cd()ef)g");
  } catch (e) {
    console.log(e.message);
  }
  try {
    validate("ab(cd()ef)g)");
  } catch (e) {
    console.log(e.message);
  }
  try {
    validate("{ab(cd()ef)g)");
  } catch (e) {
    console.log(e.message);
  }
  try {
    validate("[({)}]");
  } catch (e) {
    console.log(e.message);
  }
})();