JIYIK CN >

MongoDB is an excellent platform that is growing in popularity. Among the various features it offers, MongoDB also allows you to convert data from one type to another.

This may seem like a complex function, but it is very simple to execute.

If you are looking for a way to convert data from a string to a date, you have come to the right place.

Create a string or date data type

Before we delve into how the conversion works, it's worth explaining how strings and dates are created. Ideally, the user initially selects the data type he wants.

However, you may want to change it later. Regardless, there are a few ways you can initially create a field with a date format.

{
birth: new Date('Jun 23, 1912'),
}

So the general structure is the field name followed by a colon and then the data type.

Convert string to date in MongoDB

MongoDB does allow you to switch the data type from string to date. It is much simpler than you might expect.

All you need to do is add a few extra lines of code, and you're ready to go.

Using the toDate Operator

Of all the methods, the toDate operator is probably the one that is used most frequently. This is because it is easy to remember and simple to execute.

This operator converts the value to a date if possible.

However, if it cannot be changed to this format, it returns an error. Similarly, if the value to be converted is null or missing, the operator returns null.

It is important to note that if your MongoDB version is lower than MongoDB 4.0, you may not be able to use this method. This is a simple method using MongoDB's toDate operator.

db.collection.aggregate([
{ "$addFields": {
"created_at": {
"$toDate": "$created_at"
}
} }
])

This code will change the field stored in the required date format. As mentioned above, if there is any error or data is missing, the operator will return an error or null value.

Using conversion operators

Another way you can convert a string to a date is with the conversion operator. This works similarly to the toDate operator, except that you convert the value to a date format.

convertoperator is different because it is used for many transformations.

It is not limited to conversion from string to date. Therefore, when using the conversion operator, it is necessary to define the data type to which the value is to be converted.

This is usually done using the to operator after using the conversion operator. You can refer to the following code to understand its use better.

db.collection.aggregate([
{ "$addFields": {
"created_at": {
"$convert": {
"input": "$created_at",
"to": "date"
}
}
} }
])

This code is the same as the code executed by the toDate operator above. You can see that after specifying the convert operator, the to operator is used to specify the date format to which the value is to be converted.

Keep in mind that this operator is only available in MongoDB 4.0and newer versions.

Using the dateFromString operator

If you are using an older version of MongoDB, you can always use dateFromStringthe operator to accomplish your job. This applies to all versions of MongoDB 3.6 or newer, so you may need to update to use this operator.

dateFromStringThe operator allows you to convert a string into a date object. In addition, it has some additional features, such as options for specifying the date format and time zone.

This is a simple way to use this operator.

db.collection.aggregate([
{ "$addFields": {
"created_at": {
"$dateFromString": {
"dateString": "$created_at",
"format": "%m-%d-%Y"/* this option is only available in MongoDB 4.0. or newer versions*/
}
}
} }
])

This code will allow you to do the conversion you want. Also, if you have the right version of MongoDB you can even change the date format using the format operator.

Using the set operator

If you prefer to use an older version of MongoDB, you can still achieve the desired results by using the set operator. This is available in all MongoDB versions between MongoDB 2.6 and MongoDB 3.1, inclusive.

It is important to note that this operator is not just for converting strings to dates. Therefore, you will have to include some manual processes to get the job done.

You will have to use forEach()the method or the cursor method next()to iterate over find()the cursor returned by the method to access what you want. You must convert the desired fields to ISODATE objects in this loop.

Finally, you will update the set operator so that the string format can be updated. In the following code, xyz is a field containing a string that must be converted to a date format.

var cursor = db.collection.find({"xyz": {"$exists": true, "$type": 2 }});
while (cursor.hasNext()) {
var doc = cursor.next();
db.collection.update(
{"_id" : doc._id},
{"$set" : {"xyz" : new ISODate(doc.xyz)}}
)
};

Using ClockTime

Another approach that works in most cases is to use ClockTime. This essentially uses the ClockTime collection and find()the method to convert the string to a date format.

An example of usage is shown in the code below.

db.ClockTime.find().forEach(function(doc) {
doc.ClockInTime=new Date(doc.ClockInTime);
db.ClockTime.save(doc);
})

We hope that you can now find a way to convert strings to dates that works for you on MongoDB.