Date parameter in function

Question

I want to pass a date to a javascript function for some manipulation. The problem I am facing here is: the function is changing the actual date parameter though it works on a local parameter. Here is an example where I have mentioned my issue

var myDate = new Date();
console.log(myDate);//Result is Mon Oct 22 2018 09:40:01
function manipulate(d){
    d.setDate(d.getDate()+1);
    console.log(d);//Result is Oct 23 2018 09:40:01
    return d;
}
var result = manipulate(myDate);
console.log(result);//Result is Oct 23 2018 09:40:01 as expected.
console.log(myDate);//Result is Oct 23 2018 09:40:01. I want this to be my initial value. That is Mon Oct 22 2018 09:40:01

I guess it JS uses pass by reference if the date is used as a parameter. How can I resolve the above-mentioned issue?

Regards,

SAP Learner

Try to take a copy of date in the function as follows: var dLocalCopyFrom = new Date(d.getTime()); dLocalCopyFrom.setDate(dLocalCopyFrom.getDate()+1); This will not alter the actual date — F H, Oct 22 '18 at 09:15
Use the Date object's getTime() function to get a clone. https://stackoverflow.com/questions/1090815/how-to-clone-a-date-object-in-javascript — Ryan Pierce Williams, Oct 22 '18 at 09:16

ZeroCho · Accepted Answer · 2018-10-23T13:09:59.037

2

You have to copy it first

function manipulate(d){
    var s = new Date(d)
    s.setDate(s.getDate()+1);
    console.log(s);//Result is Oct 23 2018 09:40:01
    return s;
}

edited Oct 23 '18 at 13:09

answered Oct 22 '18 at 09:15

ZeroCho

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`new Date(d)` is sufficient. – RobG Oct 22 '18 at 11:03

Date parameter in function

1 Answers1