javascript - 为什么这段代码运行错误

Question

我正在尝试使用日期格式打印日期，例如 09/05/1998，但是当我运行代码时，我得到 081/5/1998 我做错了什么？

var c = new Date("September 5, 1998 08:45:00");

function datePrinter(){
var monthPrinter = c.getMonth();
var dayPrinter = c.getDate();
var yearPrinter = c.getFullYear();


if(monthPrinter < 10){
monthPrinter = "0" + monthPrinter;
monthPrinter = monthPrinter + 1;
}
if(datePrinter < 10){
datePrinter = "0" + dayPrinter;
} 

document.write(monthPrinter + "/" +dayPrinter + "/" + yearPrinter);


}

datePrinter();

Answer 1

当您在数字前面或后面添加字符串时，结果将成为字符串。当您递增它时，它会进行字符串连接而不是添加。您需要再次使用 parseInt() 将字符串解析为 Number。

var c = new Date("September 5, 1998 08:45:00");

function datePrinter(){
var monthPrinter = c.getMonth() + 1;
var dayPrinter = c.getDate();
var yearPrinter = c.getFullYear();

if(monthPrinter < 10){
monthPrinter = "0" + monthPrinter;
}
if(dayPrinter < 10){
dayPrinter = "0" + dayPrinter;
} 

document.write(monthPrinter + "/" +dayPrinter + "/" + yearPrinter);


}

datePrinter();