Creating a Javascript Dictionary

If you come from a Python background you're probably used to creating dictionaries and you're wondering how you would create a Javascript dictionary.

The first thing to note is a Javascript dictionary is usually called a Javascript object.

Creating an object in Javascript has the same syntax as creating a dictionary in Python.

const fruitsInventory = {
    apples: 56,
    oranges: 34,
    pears: 983,
    bananas: 13,
}

console.log(typeof fruitsInventory) // "object"

There aren't many commonly used built in methods here.

Accessing Properties on a Javascript Dictionary

const fruitsInventory = {
    apples: 56,
    oranges: 34,
    pears: 983,
    bananas: 13,
}

console.log(fruitsInventory.apples) // 56

Accessing Properties on a Nested Javascript Dictionary

const inventory = {
    fruits: {
        apples: 56,
        oranges: 34,
        pears: 983,
        bananas: 13,
    },
    vegetables: {
        cucumbers: 67,
        tomatoes: 52,
        potatoes: 12
    },
    meats: {
        poultry: {
            chicken: 124,
            turkey: 356
        },
        redMeat: {
            beef: 300,
        }
    }
}

console.log(inventory.fruits.oranges) // 34

// As of ES2020 you can use optional chaining to access a property which might not exist and it won't throw an error.
console.log(inventory.fruits.cannedGoods?.beans)

You can call methods on Object and pass in your object.

const fruitsInventory = {
    apples: 56,
    oranges: 34,
    pears: 983,
    bananas: 13,
}

console.log(Object.keys(fruitsInventory)) // ["apples", "oranges", "pears", "bananas"]
console.log(Object.values(fruitsInventory)) // [56, 34, 983, 13]

You'll also find that what you call a list in Python is usually called an array in Javascript.

I hope this was helpful.