The validParentheses function takes a string containing various types of parentheses ((), {}, []) as input and checks whether the arrangement of parentheses is valid. It returns true if the input string contains a valid arrangement of parentheses, meaning that for every opening parenthesis, there is a corresponding closing parenthesis in the cor…

validParentheses.ts

function validParentheses(str: string): boolean {
  const stack: string[] = [];
  const map: Record<string, string> = {
    '}': '{',
    ')': '(',
    ']': '[',
  };
  for (let index = 0; index < str.length; index++) {
    const char = str[index];
    if (map[char]) {
      if (stack.length > 0 && stack[0] === map[char]) {
        stack.shift();
      } else {
        stack.unshift(char);
      }
    } else {
      stack.unshift(char);
    }
  }
  return stack.length === 0;
}
console.log('{{}}()[()]', validParentheses('{{}}()[()]')); // true
console.log('{][}', validParentheses('{][}')); // false
console.log(')', validParentheses(')')); // false
console.log('{}', validParentheses('{}')); // true
console.log('()', validParentheses('()')); // true
console.log('({})', validParentheses('({})')); // true
console.log('((()))', validParentheses('((()))')); // true
console.log('[(])', validParentheses('[(])')); // false
console.log('{[()()]}', validParentheses('{[()()]}')); // true
console.log('(({[]}))', validParentheses('(({[]}))')); // true

The valid parentheses problem involves checking that:

all the parentheses are matched, i.e., every opening parenthesis has a corresponding closing parenthesis.
the matched parentheses are in the correct order​, i.e., an opening parenthesis should come before the closing parenthesis.

Algorithm
Declare an empty stack.
Push an opening parenthesis on top of the stack.
In case of a closing bracket, check if the stack is empty.
If not, pop in a closing parenthesis if the top of the stack contains the corresponding opening parenthesis.
If the parentheses are valid,​ then the stack will be empty once the input string finishes.