How to find user by username LIKE value with Mongoose.js and JavaScript?

To find user by username LIKE value with Mongoose.js and JavaScript, we use the findOne method with a regex.

For instance, we write

const name = "Peter";
model.findOne({ name: new RegExp("^" + name + "$", "i") }, (err, doc) => {
  //...
});

to call findOne to find the document with field name like the 'Peter' by setting name to a regex with name in it.

We use the i flag to search in a case insensitive manner.

We get result from doc in the callback.