In JavaScript, a constructor is a special function used to create and initialize an object instance of a class, typically invoked with the new keyword. When called, it creates a new object, binds the this keyword to this object, and returns it as the constructor's result. Constructors can define properties using parameters, allowing unique object instances, and can enrich functionality through prototypes, which add shared properties and methods across instances. While JavaScript offers built-in constructors for objects, strings, numbers, and booleans, using primitive data types is recommended for performance reasons. Additionally, tools like Rollbar can be utilized to manage and analyze errors effectively, enhancing confidence in deploying production code by automating error monitoring and triaging.