How to set a default parameter value if no argument is passed through using the switch statement condition?

I’m doing a lab exercise on VScode for an assignment and I’m unable to pass one of the Mocha test requirements. This test requires “takes in two arguments, a name and a language, and language defaults to JavaScript”. I’ve tried to default it to “Javascript” value assuming it wants a switch statement. This is the following requirements:

describe('introductionWithLanguageOptional(name, language)', function() {
  it('takes in two arguments, a name and a language, and language defaults to JavaScript', function() {
    expect(introductionWithLanguageOptional("Gracie")).toEqual("Hi, my name is Gracie and I am learning to program in JavaScript.");
  })
})

Quite frankly, I’ve confused myself.

This is what I’ve tried:

function introductionWithLanguageOptional(name, language= "Javascript"){
    switch (name, language) {
        case(name, language) :
            return `Hi, my name is ${name} and I am learning to program in ${language}.`
            break;
        default:
            return `Hi, my name is ${name} and I am learning to program in ${language}.`
    }
}

console.log(introductionWithLanguageOptional("Gracie"))

//It returns with: 
Hi, my name is Gracie and I am learning to program in undefined.