Checks if a given string has its brackets balanced

areBracketsBalanced.js

/**
 * Tests if the brackets in a given string are balanced
 * @param {string} expression - the expression string to be tested.
 */
function areBracketsBalanced(expression) {
  if (!expression) {
    return false;
  }

  /**
   * @type {Array} stack
   */
  const stack = [];

  const arePairing = (opening, closing) =>
    (opening == "(" && closing == ")") ||
    (opening == "{" && closing == "}") ||
    (opening == "[" && closing == "]");

  const isOpening = char => char == "(" || char == "[" || char == "{";
  const isClosing = char => char == ")" || char == "]" || char == "}";

  [...expression].forEach(char => {
    if (isOpening(char)) {
      stack.push(char);
    } else if (isClosing(char)) {
      // assures that closures are occuring in the correct order.
      if (!stack.length || !arePairing(stack[stack.length - 1], char)) {
        return false;
      } else {
        stack.pop();
      }
    }
  });

  return !stack.length;
}

// Test cases
console.log(Solution("(a[0]+b[2c[6]]){24+53}"));
console.log(Solution("f(e(d))"));
console.log(Solution("[()]{}([])"));
console.log(Solution("((b)"));
console.log(Solution("(c]"));
console.log(Solution("{(a[])"));
console.log(Solution("([(]"));
console.log(Solution(")("));
console.log(Solution(""));