ES6 class and ES5 function constructors are both used to create objects in JavaScript, but there are some differences between the two.

Syntax: The syntax for creating objects using ES6 classes is different from ES5 function constructors. ES6 classes use a more traditional class-based syntax, while ES5 function constructors use a constructor function with the ‘new’ keyword.

Inheritance: ES6 classes have built-in support for inheritance, using the ‘extends’ keyword to create a subclass. ES5 function constructors can also create subclasses, but it requires more complex prototypal inheritance.

Strict mode: ES6 classes are always in strict mode by default, while ES5 function constructors are not.

Default parameter values: ES6 classes allow you to set default values for parameters, while ES5 function constructors do not.