Can you explain the significance of using the fat arrow syntax as a parameter in a function invocation?

Question

Can you explain the significance of using the fat arrow syntax as a parameter in a function invocation?

I stumbled upon this code snippet on this website

import {Http} from 'angular2/http'
import {Injectable} from 'angular2/core'
@Injectable()
export class AddressBookService {
    http:Http;
    constructor(http:Http){
        console.log('Creating AddressBookService');
        this.http = http;
    }
    getEntries(){
        return this.http.get('./people.json').map(res => res.json());
    }
}

I'm struggling to grasp the purpose of res => res.json(). It appears to be a lambda function, but I can't decipher its intended use. It doesn't seem to store a variable or perform any meaningful operations.

If someone could shed some light on what this line accomplishes, it would be greatly appreciated.

lambda typescript angular

Answer 1

Answer №1

async function fetchData() {
    const response = await fetch('./people.json');
    const data = await response.json();
    return data;
}

Using ES6 arrow functions is a more concise way to define functions, as shown in the ES6 version above. However, the functionality remains the same when compared to the ES5 compatible version below:

function fetchData() {
    return this.http.get('./people.json').map(function(res) {return  res.json();});
}

The use of `map` in the code suggests that `this.http.get('./people.json')` represents a collection and the `map` method is used to iterate over each element in the collection, creating a new collection based on the result of applying a function to each element. This behavior is similar to using Array.map:

[1,2,3,4].map(x => x+1); // ==> [2,3,4,5]

Answer 2

async function fetchData() {
    const response = await fetch('./people.json');
    const data = await response.json();
    return data;
}

Using ES6 arrow functions is a more concise way to define functions, as shown in the ES6 version above. However, the functionality remains the same when compared to the ES5 compatible version below:

function fetchData() {
    return this.http.get('./people.json').map(function(res) {return  res.json();});
}

The use of `map` in the code suggests that `this.http.get('./people.json')` represents a collection and the `map` method is used to iterate over each element in the collection, creating a new collection based on the result of applying a function to each element. This behavior is similar to using Array.map:

[1,2,3,4].map(x => x+1); // ==> [2,3,4,5]

Answer 3

Answer №2

Consider this line:

fetch('./people.json').then(response => response.json());

Redesigned as follows:

function extractJsonData(response) {
    return response.json();
}

var response = fetch('./people.json');
return extractJsonData(response);

Answer 4

Consider this line:

fetch('./people.json').then(response => response.json());

Redesigned as follows:

function extractJsonData(response) {
    return response.json();
}

var response = fetch('./people.json');
return extractJsonData(response);

Answer 5

Answer №3

https://www.w3schools.com/jsref/jsref_arrows.asp

this is connected to the scope where the function is declared (the current ContactListService instance). Even though the function doesn't make use of this, it's preferable to consistently use => for clarity and reduced chances of errors in case this is utilized later on.

Answer 6

https://www.w3schools.com/jsref/jsref_arrows.asp

this is connected to the scope where the function is declared (the current ContactListService instance). Even though the function doesn't make use of this, it's preferable to consistently use => for clarity and reduced chances of errors in case this is utilized later on.

Can you explain the significance of using the fat arrow syntax as a parameter in a function invocation?

Answer №1

Answer №2

Answer №3

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