Sort array based on string transformed into date

Question

So I have an array containing reviews (which I retrieve from firebase firestore). The field 'date' is string in firestore. How can I sort the reviews in descending order based on this date? I have tried this but they are in the retrieval order.

const getReviews=async()=>{
        let reviewsClone=[];
        const q = query(collection(db, "reviews"), where("product", "==", uniqueProductName.product));
        const querySnapshot=await getDocs(q);
        querySnapshot.forEach((doc)=>{
            reviewsClone.push(doc.id);
        })

        reviewsClone.sort(function(a,b){
            return new Date(a.date) - new Date(b.date);
          });
        setReviews(reviewsClone);

    }

If the string is in ISO format, you may want to user OrderBy in the firebase query instead. — maxpsz
– maxpsz, Commented May 21, 2022 at 14:21

Igor Loskutov · Accepted Answer · 2022-05-21 13:57:05Z

1

Could you try this? It's likely that you are sorting an array of strings reviewsClone currently, which all have .date prop undefined, therefore .sort has no effect.

const getReviews=async()=>{
        let reviewsClone=[];
        const q = query(collection(db, "reviews"), where("product", "==", uniqueProductName.product));
        const querySnapshot=await getDocs(q);
        querySnapshot.forEach((doc)=>{
            reviewsClone.push(doc);
        })

        reviewsClone.sort(function(a,b){
            return new Date(a.date) - new Date(b.date);
          });
        setReviews(reviewsClone.map(c => c.id));

    }

answered May 21, 2022 at 13:57

Igor Loskutov

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3 Comments

ALL Over a year ago

yes, I think you're right. but this still not works

Igor Loskutov Over a year ago

It's not one error but several, then. Probably the answer above mine would help. Also check that new Date(a.date) and new Date(b.date) return correct dates indeed.

ALL Over a year ago

ok so I had to change the date format from my db from 'dd/mm/yyyy' to 'mm/dd/yyyy' and it works now (also is b.date - a.date)

Charchit Kapoor · Accepted Answer · 2022-05-21 14:06:39Z

0

Assuming that all the data is valid, and contains the date key. Your sort function is incorrect. To sort in descending order, your sort function should look like this:

reviewsClone.sort(function(a,b){
        return new Date(b.date) - new Date(a.date);
      });

This documentation should be helpful.

answered May 21, 2022 at 14:06

Charchit Kapoor

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