Objects and Data Structures

Introduction

Info

This is based on Ryan McDermott's clean-code-javascript that was written in December 2016. Some of the principles may be very JavaScript specific. Most of the principles will apply to all languages and this is a good working base to start from.

Use getters and setters

Using getters and setters to access data on objects could be better than simply looking for a property on an object. "Why?" you might ask. Well, here's an unorganized list of reasons why:

• When you want to do more beyond getting an object property, you don't have to look up and change every accessor in your codebase.
• Makes adding validation simple when doing a set.
• Encapsulates the internal representation.
• Easy to add logging and error handling when getting and setting.
• You can lazy load your object's properties, let's say getting it from a server.

Bad

function makeBankAccount() {
    // ...

    return {
        balance: 0
    // ...
    };
}

const account = makeBankAccount();
account.balance = 100;

Good

function makeBankAccount() {
    // this one is private
    let balance = 0;

    // a "getter", made public via the returned object below
    function getBalance() {
        return balance;
    }

    // a "setter", made public via the returned object below
    function setBalance(amount) {
        // ... validate before updating the balance
        balance = amount;
    }

    return {
        // ...
        getBalance,
        setBalance
    };
}

const account = makeBankAccount();
account.setBalance(100);

Make objects have private members

This can be accomplished through closures (for ES5 and below).

Bad

const Employee = function(name) {
    this.name = name;
};

Employee.prototype.getName = function getName() {
    return this.name;
};

const employee = new Employee("John Doe");
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
delete employee.name;
console.log(`Employee name: ${employee.getName()}`); // Employee name: undefined

Good

function makeEmployee(name) {
    return {
        getName() {
            return name;
        }
    };
}

const employee = makeEmployee("John Doe");
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe
delete employee.name;
console.log(`Employee name: ${employee.getName()}`); // Employee name: John Doe