输出什么？

const groceries = ["banana", "apple", "peanuts"];

if (groceries.indexOf("banana")) {
  console.log("We have to buy bananas!");
} else {
  console.log(`We don't have to buy bananas!`);
}

我们传递了一个状态 groceries.indexOf("banana") 给if条件语句。groceries.indexOf("banana") 返回 0， 一个 falsy 的值。因为if条件语句的状态为 falsy，else 块区内的代码执行，并且 We don't have to buy bananas! 被输出.