Why is this an issue?

By convention, constructor function names should start with an upper case letter as a reminder that they should be called with the new keyword.

A function is considered to be a constructor when it sets all of its arguments as object properties, and returns no value.

Noncompliant code example

function person (firstName, middleInitial, lastName) {  // Noncompliant
  this.firstName = firstName;
  this.middleInitial = middleInitial;
  this.lastName = lastName;
}

Compliant solution

function Person (firstName, middleInitial, lastName) {
  this.firstName = firstName;
  this.middleInitial = middleInitial;
  this.lastName = lastName;
}