Here is my solution to this problem:
/**
* @param {string} s
* @return {string}
*/
var minRemoveToMakeValid = function(s) {
const stack = [];
const charArray = s.split("");
const rightBracketsToRemove = [];
for (let i=0;i<charArray.length;i++) {
if (charArray[i] === '(') {
stack.push(i);
} else if (charArray[i] === ')' && stack.length > 0) {
stack.pop();
} else if (charArray[i] === ')') {
charArray[i] = '';
}
}
while (stack.length > 0) {
const i = stack.pop();
charArray[i] = '';
}
return charArray.join('');
};