How does this function work in javascript?

Question

I need your help in understanding below codes.

map<U>(mapFunction: (task: Task, index: number)=> U) {
        return this.tasks.map(mapFunction);
}

forEach<U>(mapFunction: (task: Task, index: number)=> U) {
        return this.tasks.forEach(mapFunction);
 }

Can anyone explain me how these codes work. I'm trying to search it but failed. I know there is a term for using these codes. I just don't get the term

Answer 1

It's nothing but fat arrow in type script. this gets convert to java script using transpilers and Babel is one of the popular for this job

more information on fat arrow

Answer 2

Here is at least some information if not all.

Link to explanation

It's called a

javascript map function

In short: It itererates over array elements and calling functions on them