for each token in the reversed postfix expression:
  if token is an operator:
    push token onto the operator stack
    pending_operand ← False
  else if token is an operand:
    operand ← token
    if pending_operand is True:
      while the operand stack is not empty:
        operand_1 ← pop from the operand stack
        operator ← pop from the operator stack
        operand ← evaluate operator with operand_1 and operand
    push operand onto the operand stack
    pending_operand ← True
result ← pop from the operand stack

const   rpn = ["-", "+", "+", 1, 1, 2, "*", 3, "/", "-", "+", 1, 1, 7, 15];
const   operator_Stack = [];
const   operand_Stack = [];
var     pending = false;

for (i = 0; i < rpn.length; i++) {
    const   token = rpn[i];
    if (typeof token === "string") {
        operator_Stack.push(token);
        pending = false;
    } else {
        var operand = token;
        if (pending) {
            while (operand_Stack.length > 0) {
                let operand_1 = operand_Stack.pop();
                let operator = operator_Stack.pop();
                operand = eval(operand_1 + " " + operator + " " + operand);
            }
        }
        operand_Stack.push(operand);
        pending = true;
    }
}
console.log(operand_Stack.pop());