Section 1.1: Using Objects to Create Associative Arrays

One effective way to establish associative arrays is through JavaScript objects. This method allows dynamic removal of object properties, where the property name acts as the key and the corresponding value serves as the value.

For example, you can create a dictionary object as follows:

const dictionary = {};

dictionary.a = 1;

dictionary.b = 2;

console.log(dictionary);

This results in the dictionary object displaying {a: 1, b: 2}.

Additionally, property names can be assigned using string literals in square brackets:

const dictionary = {};

dictionary['a'] = 1;

dictionary['b'] = 2;

console.log(dictionary);

This capability enables dynamic addition of property names in your code.

To loop through the properties of the object, you can utilize the Object.keys, Object.values, or Object.entries methods.

• Object.keys generates an array containing the keys of the object.
• Object.values produces an array of the object's values.
• Object.entries returns an array of key-value pairs.

Here’s how you can use these methods:

const dictionary = {};

dictionary.a = 1;

dictionary.b = 2;

for (const key of Object.keys(dictionary)) {

console.log(key, dictionary[key]);

}

This will output:

a 1

b 2

In this loop, the variable key represents each key being iterated over.

You can also loop through the values as follows:

for (const value of Object.values(dictionary)) {

console.log(value);

}

This will yield:

1

2

Lastly, to iterate over key-value pairs:

for (const [key, value] of Object.entries(dictionary)) {

console.log(key, value);

}

This destructures the key and value from the iterated array, resulting in:

a 1

b 2

Since the Object.keys, Object.values, and Object.entries methods return arrays, you can easily determine their length using the .length property.

Section 1.2: Utilizing Maps for Associative Arrays

With ES6, the Map constructor provides an alternative approach to creating associative arrays or hashes. Here’s a simple example:

const map = new Map();

map.set('a', 1);

map.set('b', 2);

In this case, the set method is called with the key and value to add an entry. You can then iterate through the map using a for-of loop:

for (const [key, value] of map) {

console.log(key, value);

}

To retrieve a value based on its key, use the get method:

console.log(map.get('a'));

Passing in 'a' returns 1, as expected.

To ascertain the size of the map, simply use the size property:

console.log(map.size);

This will display 2 in the console.