Reuse/Abstract filter function body to enforce DRY principle?

[dhern023]

I’m using the Simple Books API to practice composing tests in Postman.

[
    {
        "id": 1,
        "name": "The Russian",
        "type": "fiction",
        "available": true
    },
    {
        "id": 2,
        "name": "Just as I Am",
        "type": "non-fiction",
        "available": false
    },
    {
        "id": 3,
        "name": "The Vanishing Half",
        "type": "fiction",
        "available": true
    },
    {
        "id": 4,
        "name": "The Midnight Library",
        "type": "fiction",
        "available": true
    }
]

Almost every filter example I’ve seen relies on a hard-coded attribute equalling a hard-coded value.

let response = pm.response.json();

let nonfiction_books = response.filter( (book) => book['available'] === true )

Is there any way I can abstract that filter body out to a reusable function? How would I use it?

function check_key_value(json_, key, value)
{
    json_[key] === value;
}

let books_available = response.filter( ? )

[anon22924398]

Not clear to me, maybe you could wrap filter in a function?

const myFilter = (array, key, value)=> array
.filter(obj=>obj[key]===value)

For example

myF(a,"available",true)

//returns
[
  { id: 1, name: 'The Russian', 
type: 'fiction', available: true },
  {
    id: 3,
    name: 'The Vanishing Half',
    type: 'fiction',
    available: true
  },
  
{
    id: 4,
    name: 'The Midnight Library',
    type: 'fiction',
    available: true
  }
]

[dhern023]

(post deleted by author)

[dhern023]

Thanks. I had to rewrite it so I could use it.

function select_key_value(array, key, value)
{ 
   return array.filter( (obj) => obj[key]===value );
}

let books_available = select_key_value(response, 'available', true);

What is the functional difference between the const and the function definitions? Are const’s like lambdas?

[anon22924398]

If I get the question these are the basic differences…

Named and unnamed function expressions (FE)

Named FE can be executed before definition

hello() // logs hello!
function hello(){
console.log('hello')
}
hello()//also logs

Unnamed FE (anonymous function)

They won’t be available before definition.

result(1,2) //error
let result = function (p1,p2) {console.log(p1*p2)}
result(1,2)

They can be executed automatically IIFE (immediately executed function expression) :

let result = (function (p1,p2) {return 1*2})(1,2)
console.log(result) // 2

So those are functions called with function keyword, named and unnamed.

Arrow functions are always anonymous, and a compact version of an anonymous function. They look nice but have some limitations.

let arrowResult = (p1,p2) => p1*p2