CODEWITHSUNDEEP
javascriptreference
slinkhi
slinkhi

Reputation: 989

javascript - how to NOT assign by reference

Okay consider this bit of code:

var d1 = new Date();
var d2 = d1;

d2.setDate(d2.getDate()+1);
alert(d1 + "\n" + d2);

Even though I call setDate() on d2, d1 is also being incremented. I understand this to be because d1 is assigned to d2 by reference. My question is...how do I NOT do this, so that .setDate() only gets applied to d2?

Upvotes: 4

Views: 752

Answers (3)

Andrew Clear
Andrew Clear

Reputation: 8020

Think this should work:

var d1 = new Date();
var d2 = new Date();
d2.setDate(d1.getDate());

d2.setDate(d2.getDate()+1);
alert(d1 + "\n" + d2);

Upvotes: 0

Adam Mihalcin
Adam Mihalcin

Reputation: 14468

You need

var d2 = new Date(d1.getTime());

See How to clone a Date object in JavaScript for more details.

Upvotes: 1

josh3736
josh3736

Reputation: 145002

In JavaScript, all objects are assigned to variables 'by reference'. You need to create a copy of the object; Date makes it easy:

var d2 = new Date(d1);

This will create a new date object copying d1's value.

Upvotes: 10

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