Extract Function.md

Extract function

Why?

You have more lines in the code which can be grouped together.

Benefits:

• the code is more readable: less code to read in that function
• avoid code duplication
• isolate independent code, more easy to write unit tests

What?

Move the code which can be grouped to a new function/method and replace the old code with a call to that method.

How?

• Create a new function
• Copy the code to that function
• Replace the old code with a call to that function

Sample

Before

/*
class Person{
    constructor(firstName, lastName, dateOfBirth){
        this.firstName = firstName;
        this.lastName = lastName;
        this.dateOfBirth = dateOfBirth;
    }

    getAge(){
        const diffMiliseconds = Date.now() - Date.parse(this.dateOfBirth);
        return new Date(diffMiliseconds).getFullYear() - 1970;
    }
*/
    printPerson(){
        let age = this.getAge();

        console.log(`name: ${this.firname}`);
        console.log(`name: ${this.lastName}`);
        console.log(`name: ${age}`);
    }
/*
}

module.exports = Person;
*/

/*
class Person{
    constructor(firstName, lastName, dateOfBirth){
        this.firstName = firstName;
        this.lastName = lastName;
        this.dateOfBirth = dateOfBirth;
    }

    getAge(){
        const diffMiliseconds = Date.now() - Date.parse(this.dateOfBirth);
        return new Date(diffMiliseconds).getFullYear() - 1970;
    }
*/
    printPerson(){
        let age = this.getAge();

        this.showDetails(age);
    }

    showDetails(age){
        console.log(`name: ${this.firname}`);
        console.log(`name: ${this.lastName}`);
        console.log(`name: ${age}`);
    }
/*
}

module.exports = Person;
*/