How to use a Map for Character Matching In Javascript

This method uses a stack and a Map to match opening and closing brackets. As characters are processed, opening brackets are pushed onto the stack. When a closing bracket is encountered, it is checked against the stack’s top. The string is valid if the stack is empty.

Example: In this example The function isValidParentheses checks if a given string of parentheses is valid. It utilizes a stack and a map to match opening and closing parentheses. The examples demonstrate its correctness.

JavaScript

function isValidParentheses(s) {
    const stack = [];
    const matchingBrackets = new Map([
        ['(', ')'],
        ['{', '}'],
        ['[', ']']
    ]);

    for (let char of s) {
        if (matchingBrackets.has(char)) {
            stack.push(char);
        } else {
            if (stack.length === 0 || matchingBrackets.get(stack.pop()) !== char) {
                return false;
            }
        }
    }

    return stack.length === 0;
}

console.log(isValidParentheses("(){}[]")); 
console.log(isValidParentheses("([{}])")); 
console.log(isValidParentheses("(]"));

Output

true
true
false

JavaScript Program to Check Valid Parentheses Using String

In this article, we will learn how we can check valid parentheses of a string, and write a program to check whether the pairs and order of “{ “, ” } “, “(“, “)”, “[“, “]” in the string expression is right or not.

Example:

Input: exp = "[()][()()]()" 
Output: True.
Explanation: all of the brackets are properly formed.
Input: exp = "[(])"
Output: False
Explanation: The first and fourth brackets are not balanced because there is a closing ']' before the final '('.