实施例

Question

我想更改javaScript中的日期格式，我发现这个代码是＆＃34; Mike Christensen＆＃34;这非常好。但我的问题是在 var month line 3 的javascript数组代码中使用两个括号的含义是什么。

var mydate = new Date(form.startDate.value);
var month = ["January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"]    [mydate.getMonth()];
var str = month + ' ' + mydate.getFullYear();

Answer 1

他使用从mydate.getMonth（）获取月份数的月份数字索引月份数组

在这段代码中，mydate.getMonth（）是11，因为他索引月份数月[11]将是12月

＆＃13;

var mydate = new Date();
console.log(mydate.getMonth());
var month = ["January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"]    [mydate.getMonth()];
console.log(month);
var str = month + ' ' + mydate.getFullYear();

＆＃13;

希望你理解

Answer 2

第一对括号是创建数组，请将其视为

var month = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]

下一对括号是按索引检索数组的操作。

someArr[index]

在你的情况下

month[11]

就是这样，作者只是通过索引获取刚刚创建的数组的元素，其中index是从另一个变量中提取的。

Answer 3

执行此操作：使用先前声明的数组中的元素来初始化var月份是一种非常便宜的方式...（可以节省你多写一行但是恕我直言会减少代码的可读性......）所以打破了这个：

var month = ["January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"]    [mydate.getMonth()];

与

相同

var monthOptionsArray = ["January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"];

var monthIndex =  mydate.getMonth();
var monthActual =  monthOptionsArray[monthIndex];

实施例

var mydate = new Date();
console.log(mydate.getMonth());
var month = ["January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"];    monthI = month[1];
console.log(monthI);
var str = month + ' ' + mydate.getFullYear();

在javascript数组中使用两个括号是什么意思

3 个答案:

实施例