String Passed As Function Parameter Is Undefined

When I pass a string to a function as a parameter, it returns undefined. Why is that? let a = 'b'; let test = (a) => console.log(a); test(); // undefined

Solution 1:

When you call test(); you aren't putting anything between ( and ), so you aren't passing any parameters.

When you defined test (with (a) =>) you created a local variable a that masks the global variable with the same name.

To pass a you have to actually pass it: test(a).

Solution 2:

Why is that?

Because you don't pass any argument. Try the following:

test(a);

The following definition:

lettest = (a) => console.log(a);

is like the following:

functiontest(a){
    console.log(a);
}

So when you call test, without passing any argument the value of a would be undefined.