ES6 逆波兰表达式

Question

var evalRPN = function (tokens) {
  // 定义一个栈用来存放数据
  let stack = [];
  for (item of tokens) {
    switch (item) {
      case ("+"):
        stack.push(Number(stack.pop()) + Number(stack.pop()));
        break;
      case ("-"):
        stack.push(Number(parseInt(-stack.pop())) + Number(parseInt(stack.pop())));
        break;
      case ("*"):
        stack.push(Number(parseInt(stack.pop())) * Number(parseInt(stack.pop())));
        break;
      case ("/"):
        let right = parseInt(stack.pop());
        stack.push(parseInt(stack.pop() /
          right));
        break;
      default:
        stack.push(item);
        break;
    }
  }
  return stack.pop();
}
var data = ["2", "1", "+", "3", "*"];
console.log(evalRPN(data));