what is select in mongoose documents code example

Example: mongoose select

// include a and b, exclude other fields
query.select('a b');
// Equivalent syntaxes:
query.select(['a', 'b']);
query.select({ a: 1, b: 1 });

// exclude c and d, include other fields
query.select('-c -d');

// Use `+` to override schema-level `select: false` without making the
// projection inclusive.
const schema = new Schema({
  foo: { type: String, select: false },
  bar: String
});
// ...
query.select('+foo'); // Override foo's `select: false` without excluding `bar`

// or you may use object notation, useful when
// you have keys already prefixed with a "-"
query.select({ a: 1, b: 1 });
query.select({ c: 0, d: 0 });