Find index of closing bracket for a given opening bracket in an expression

    // Javascript program to find index of closing
      // bracket for given opening bracket.
      class Stack {
        constructor() {
          this.items = [];
        }

        // add element to the stack
        push(element) {
          return this.items.push(element);
        }

        // remove element from the stack
        pop() {
          if (this.items.length > 0) {
            return this.items.pop();
          }
        }

        // view the last element
        top() {
          return this.items[this.items.length - 1];
        }

        // check if the stack is empty
        isEmpty() {
          return this.items.length == 0;
        }

        // the size of the stack
        size() {
          return this.items.length;
        }

        // empty the stack
        clear() {
          this.items = [];
        }
      }

      // Function to find index of closing
      // bracket for given opening bracket.
      function test(expression, index) {
        var i;

        // If index given is invalid and is
        // not an opening bracket.
        if (expression[index] != "[") {
          console.log(expression + ", " + index + ": -1");
          return;
        }

        // Stack to store opening brackets.
        let st = new Stack();
        //stack <int> st;

        // Traverse through string starting from
        // given index.
        for (i = index; i < expression.length; i++) {
          // If current character is an
          // opening bracket push it in stack.
          if (expression[i] == "[") st.push(expression[i]);
          // If current character is a closing
          // bracket, pop from stack. If stack
          // is empty, then this closing
          // bracket is required bracket.
          else if (expression[i] == "]") {
            st.pop();
            if (st.isEmpty()) {
              console.log(expression + ", " + index + ": " + i);
              return;
            }
          }
        }

        // If no matching closing bracket
        // is found.
        console.log(expression + ", " + index + ": -1");
      }

      // Driver Code

      test("[ABC[23]][89]", 0); // should be 8
      test("[ABC[23]][89]", 4); // should be 7
      test("[ABC[23]][89]", 9); // should be 12
      test("[ABC[23]][89]", 1); // No matching bracket

      // This code is contributed by satwiksuman