Filter documents based on filter function

[Muhammad Tayyab Sheikh]

Hi!
In mongoose we can search Schema using particular values of a  field such as:

schema.findOne({field: 'abcd'}); 

But I want to pass a custom filter function so  if that filter function returns true only the that sub document is selected otherwise not. For example:

schema.findOne(function (document) {
if(condition on document) {
    return true; //Yes select this element
}
else {
    return false; // No don't select this document
}
});

[Richard Bateman]

You can do that using $where, but it's not very efficient and can't use indexes.

See https://docs.mongodb.com/manual/reference/operator/query/where/

e.g.

schema.findOne({$where: "return (condition on this);"});

You'd be better off using $expr though as it's more efficient and can probably do what you need.

Richard

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