minRemoveToMakeValid.js

var minRemoveToMakeValid = function(s) {
    // Convert the string to an array to facilitate removal of characters
    let chars = s.split('');
    
    // Stack to keep track of indices of opening parentheses
    let stack = [];
    
    // Iterate through the characters of the string
    for (let i = 0; i < chars.length; i++) {
        // If the character is an opening parenthesis, add its index to the stack
        if (chars[i] === '(') {
            stack.push(i);
        } 
        // If the character is a closing parenthesis
        else if (chars[i] === ')') {
            // If stack is not empty and the top of the stack corresponds to an opening parenthesis,
            // remove the opening parenthesis index from the stack
            // Otherwise, mark the closing parenthesis for removal by replacing it with an empty string
            if (stack.length !== 0) {
                stack.pop();
            } else {
                chars[i] = '';
            }
        }
    }
    
    // Mark the remaining opening parentheses indices in the stack for removal
    while (stack.length !== 0) {
        chars[stack.pop()] = '';
    }
    
    // Join the characters array back into a string and return
    return chars.join('');
};