Minimum Remove to Make Valid Parentheses
var minRemoveToMakeValid = function(str) {
str = str.split("");
let stack = [];
for(let i = 0; i<str.length; i++){
if(str[i]==="(")
stack.push(i);
else if(str[i]===")"){
if(stack.length) stack.pop();
else str[i]="";
}
}
for(let i of stack) str[i] = "";
return str.join("");
}