javascript function to get all the days of a week

Question

I am trying to get an array of all days in a week like today is Aug 1st so i need to get an array of this week which will look like

['2019-07-28' ,'2019-07-29', '2019-07-30', '2019-07-31', '2019-08-01', '2019-08-02', '2019-08-03']

in order to achieve this i wrote the following code

var week_list = []
const today = new Date()
week_list.push(today.toISOString().substring(0,10))
var counter = today.getDay()
// get next 
var next_day = today
for(var i = counter;i<6;i++){
    next_day.setDate(next_day.getDate()+1)
    week_list.push(next_day.toISOString().substring(0,10))
}
// get prev 
var prev_day = today
for(var i = counter;i>0;i--){
    prev_day.setDate(prev_day.getDate()-1)
    week_list.push(prev_day.toISOString().substring(0,10))
}   

console.log(week_list)

output

[ '2019-08-01', '2019-08-02', '2019-08-03', '2019-08-02', '2019-08-01', '2019-07-31', '2019-07-30']

i am getting a different output instead of what i was expecting, the variable today change automatically when i try to update the next_day variable. Is this common under javascript else am i doing anything wrong.

@JstnPwll's answer is correct: `next_day`, `today`, and `prev_day` all point to the same underlying object; by changing one, you are also changing the others. — RWRkeSBZ, Aug 01 '19 at 16:18
I'd also like to point out that none of the codes here, either your own or the answers are going to give the exact output you asked for. — Anurag Srivastava, Aug 01 '19 at 16:19
when i follow the @JstnPwl's instruction i am getting the output which i was expecting — skid, Aug 01 '19 at 16:22

score 3 · Answer 1 · answered Aug 01 '19 at 16:14

3

next_day is a reference to the same object that today references. The underlying date object is the same. If you want two different objects, you should construct a new date.

var next_day = new Date()
...
var prev_day = new Date()

answered Aug 01 '19 at 16:14

JstnPwll

8,585
2
33
56

Thanks, This one work – skid Aug 01 '19 at 16:16

Nicolae Maties · Accepted Answer · 2019-08-01T16:20:01.663

0

const dates = (current) => {
    const week = []; 
    current.setDate((current.getDate() - current.getDay() +1));
    for (var i = 0; i < 7; i++) {
        week.push(
            new Date(current).toISOString().substring(0,10)
        ); 
        current.setDate(current.getDate() +1);
    }
    return week; 
}
console.log(dates(new Date()));

edited Aug 01 '19 at 16:20

answered Aug 01 '19 at 16:16

Nicolae Maties

2,476
1
16
26

Can explain rather than ask? – Ele Aug 01 '19 at 16:17
Further, can you state that your approach is mutating the param current – Ele Aug 01 '19 at 16:17
you are code gets the next 7 days from the given date, i need the current 7 days of the week from any given date – skid Aug 01 '19 at 16:18
Updated for any given date. You can call the dates function with any given date. Ex: `dates(new Date(2018, 8,8)` – Nicolae Maties Aug 01 '19 at 16:20
1

Yeah this one works – skid Aug 01 '19 at 16:23
Code only answers aren't helpful. Your answer should explain why the OP has their issue and how your code fixes it. Your code doesn't fix the OP's issue as it modifies the Date passed to it. – RobG Aug 02 '19 at 08:06

javascript function to get all the days of a week

2 Answers2