Variables Back

1. Always use const

• Always use const to declare variables. Not doing so will result in global variables. We want to avoid polluting the global namespace.

/**
 * bad
 */
hero = new Hero();

/**
 * good
 */
const hero = new Hero();

2. Use one const declaration per variable

• Eslint rules tags: one-var

the reason is that it's easier to add new variable declaration, and you don't have to worry about swapping out a ; or ,.

/**
 * bad
 */
const items = getItems(),
    goSportsTeam = true,
    dragonball = 'z';

/**
 * bad
 */
 const items = getItems(),
    goSportsTeam = true;
    dragonball = 'z';

/**
 * good
 */
const items = getItems();
const goSportsTeam = true;
const dragonball = 'z';

3. Group all the const and let

• To group all your const and let together.

the reason is that it's helpful to find when later on you need to assign a variable depending on one of the previous assigned variables.

/**
 * bad
 */
let i;
const items = getItems();
let dragonball;
const goSportsTeam = true;
let len;

/**
 * good
 */
const items = getItems();
const goSportsTeam = true;
let i;
let dragonball;
let len;

4. Place yur variables in a reasonable place

• Assign variables when necessary, and place them in a reasonable place.

the reason is that both let and const are block scoped.

/**
 * bad
 */
function (hasName) {
    const name = getName();

    if (!hasName) {
        return false;
    }

    this.setFirstName(name);

    return true;
}

/**
 * good
 */
function (hasName) {
    if (!hasName) {
        return false;
    }

    const name = getName();
    this.setFirstName(name);

    return true;
}