I'm trying to understand what this code is doing, it's from a nodejs. I don't understand what is this structure is doing
return({object}={})=>{more code}
you can find the repository here: https://github.com/howardmann/clean-node/blob/master/models/teacher/teacher.js
let buildMakeTeacher = function(teacherValidator) {
return ({
name,
subject,
tenure = false
} = {}) => {
let {error} = teacherValidator({name, subject, tenure})
if (error) throw new Error(error)
return {
getName: () => name,
getSubject: () => subject,
isTenure: () => tenure
}
}
}In addition to answer by @Sarkar, the amount of curly braces here may shock you. The point of others (that don't declare a scope) is object destructuring. Breaking down:
let {error} = teacherValidator({name, subject, tenure})
This line takes object returned by teacherValidator and extracts a key named error from it. If it returned, say, {error: 'Fail', errorcode: 1}, then error is assigned to 'Fail'.
return ({
name,
subject,
tenure = false
} = {}) => { doSomething(); }
This creates an anonymous function with complex argument handling. It is (by calling result, implementation should differ) equivalent to:
return function(params={}) {
let {name, subject, tenure=false} = params;
doSomething();
}
This function:
name and subject keys from it (undefined if not present) and tenure key (false if missing).It's a anonymous function
this
(object)=>{more code}
is equivalent to this
function functionName(object){
moreCode
}
your code example is a function called buildMakeTeacher which is returning an anonymous function which returns an object
Read about closure and curry a bit it will give you a better perspective.
But basically that means this function returns a new function which returns an object with callable actions.
So to call it you should do something like buildMakeTeacher(someValidstor)({name: “foo”, subject: “bar”}).getSubject()