为什么我的 if-else 语句不能使用 OR ( | | ) 来工作？

Question

当我运行该程序时，控制台给出一个错误，指出“星期日”（和“星期六”，基于用户输入）不存在。我在 if 语句中尝试了多种带括号的组合，但没有任何效果。

var day = prompt("Enter a day of the week.");

console.log("Day is: " + day);

//if user input is equal to Sunday OR user input is equal to Saturday,

if (getText(day) == "Sunday" || getText(day) == "Saturday") {

  console.log("It's the weekend!");

} else {

  console.log("Can't wait for the weekend to get here.");

}

Answer 1

您应该删除它getText，它将正常工作：var day = prompt('Enter a day of the week.');console.log('Day is: ' + day);if (day == 'Sunday' || day == 'Saturday') {  console.log("It's the weekend!");} else {  console.log("Can't wait for the weekend to get here.");}

Answer 2

如果用户单击“确定”或单击“取消”，该prompt()函数始终返回 a 。在您的情况下，只要您输入一些内容并单击“确定”，就会出现一个字符串，可能是或。stringnullday"Sunday""Saturday"但是，如果您希望将大写字母和小写字母视为相同，例如"sunday"相当于"Sunday"，则应使用toLowerCase()ortoUpperCase()方法来确保两个字符串要么全部小写，要么全部大写。像下面这样：var day = prompt("Enter a day of the week.");console.log("Day is: " + day);//if user input is equal to Sunday OR user input is equal to Saturday,if (day.toLowerCase() == "sunday" || day.toLowerCase() == "saturday") {  console.log("It's the weekend!");} else {  console.log("Can't wait for the weekend to get here.");}