Javascript Javascript日期变量赋值
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Javascript date variable assignment
提问by railOne
var date1 = new Date();
date1.setFullYear(2011, 6, 1);
// 2011-07-01, ok
console.log(date1);
// set date2 the same date as date1
var date2 = date1;
// ...
// now I'm gonna set a new date for date2
date2.setFullYear(2011, 9, 8);
// 2011-10-08, ok
console.log(date2);
// 2011-10-08, wrong, expecting 2011-07-01
// I didn't assign a new date to date1
// WHY is date1 changed?
console.log(date1);
回答by SergeS
Date is object , so it is assigned as reference - simple approach is
日期是对象，因此将其分配为引用-简单的方法是
date2 = new Date( date1 );
回答by davin
Both date variables are just references to the same date object in memory. So you need date2to be a cloneof date1. Change:
两个日期变量都只是对内存中同一个日期对象的引用。所以，你需要date2成为一个克隆的date1。改变：
var date2 = date1;
to this:
对此：
var date2 = new Date(date1.getTime());
回答by cwallenpoole
JavaScript uses pass by reference for Dates* (as well as all non-primitives -- var o = {}; var j = o; j.foo = 1; console.log(o.foo); //1. On the other hand, for Numbers, Strings, and Booleans var o = 0; var j = o; j++; console.log(j); // 0), so that is expected behavior.
JavaScript 对 Dates* （以及所有非原始类型 -- var o = {}; var j = o; j.foo = 1; console.log(o.foo); //1。另一方面，对于 Numbers、Strings 和 Booleans var o = 0; var j = o; j++; console.log(j); // 0）使用按引用传递，因此这是预期的行为。
If you need to copy a date you can always
如果您需要复制日期，您可以随时
var date2 = new Date( date1.getTime() );
* Please see comments to understand why this is not entirely correct.
* 请参阅评论以了解为什么这不完全正确。
回答by Guest
date2It's a reference to date1.
date2这是对date1.
To achieve the expected results, do the following:
要达到预期的结果，请执行以下操作：
var date1 = new Date();
date1.setFullYear(2011, 6, 1);
var date2 = new Date();
date2.setTime(date1.valueOf());
回答by yzorg
Variation of @SergeS's answer, but Date() objects in js coerce to number, so you don't need getTime():
@SergeS 答案的变化，但 js 中的 Date() 对象强制为数字，因此您不需要 getTime()：
// general case
var dateValueCopy = new Date(date1);
And restated with OP variable names:
并用 OP 变量名称重述：
var date2 = new Date(date1);
回答by Anadi Kumar
<html lang="en">
<head>
<script>
function getDateDiff(time1, time2) {
var str1= time1.split('/');
var str2= time2.split('/');
var t1 = new Date(str1[2], str1[0]-1, str1[1]);
var t2 = new Date(str2[2], str2[0]-1, str2[1]);
var diffMS = t1 - t2;
console.log(diffMS + ' ms');
var diffS = diffMS / 1000;
console.log(diffS + ' ');
var diffM = diffS / 60;
console.log(diffM + ' minutes');
var diffH = diffM / 60;
console.log(diffH + ' hours');
var diffD = diffH / 24;
console.log(diffD + ' days');
alert(diffD);
}
//alert(getDateDiff('10/18/2013','10/14/2013'));
</script>
</head>
<body>
<input type="button" onclick="getDateDiff('10/18/2013','10/14/2013')" value="clickHere()" />
</body>
</html>
回答by Alex K.
You need to create a copy of date1, currently date1and date2refer to the same date object.
您需要创建date1, 当前的副本date1并date2引用相同的日期对象。
var date2 = new Date(date1.valueOf());
