How do you iterate over a Map object in JavaScript?

In JavaScript, a Map object is a collection of key-value pairs where each key can be of any type.

The keys in a Map object are unique, and the values can be of any type. Iterating over a Map object can be done in various ways depending on the requirements.

Here are some examples of iteration over a Map object:

Method 1: Using the `for...of` loop:

The for...of loop is a convenient way to iterate over a Map object. It allows you to iterate over the keys or the values or both.

For example:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");
myMap.set("key3", "value3");

// Iterate over the keys
for (let key of myMap.keys()) {
  console.log(key);
}

// Iterate over the values
for (let value of myMap.values()) {
  console.log(value);
}

// Iterate over both keys and values
for (let entry of myMap) {
  console.log(entry[0], entry[1]);
}

Output:

key1
key2
key3
value1
value2
value3
key1 value1
key2 value2
key3 value3

Method 2: Using the `forEach()` method:

The forEach() method is another way to iterate over a Map object. It allows you to execute a function for each key-value pair in the Map object.

For example:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");
myMap.set("key3", "value3");

// Iterate over the key-value pairs
myMap.forEach(function (value, key) {
  console.log(key, value);
});

Output:

key1 value1
key2 value2
key3 value3

Method 3: Using the `entries()` method and a while loop:

The entries() method returns an iterator object that contains the key-value pairs of the Map object. You can iterate over this iterator object using a while loop.

For example:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");
myMap.set("key3", "value3");

// Get the iterator object for the Map object
let entries = myMap.entries();

// Iterate over the key-value pairs using a while loop
let currentEntry = entries.next();
while (!currentEntry.done) {
  console.log(currentEntry.value[0], currentEntry.value[1]);
  currentEntry = entries.next();
}

Output:

key1 value1
key2 value2
key3 value3

Method 4: Using the `Array.from()` method:

The Array.from() method can be used to create a new array from an iterable object, including a Map object. This new array can then be iterated over using a for...of loop.

For example:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");
myMap.set("key3", "value3");

// Create a new array from the Map object
let entriesArray = Array.from(myMap);

// Iterate over the key-value pairs in the array
for (let [key, value] of entriesArray) {
  console.log(key, value);
}

Output:

key1 value1
key2 value2
key3 value3

Method 5: Using the spread operator

The spread operator (...) can also be used to create a new array from a Map object. This new array can then be iterated over using a for...of loop.

For example:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");
myMap.set("key3", "value3");

// Create a new array from the Map object using the spread operator
let entriesArray = [...myMap];

// Iterate over the key-value pairs in the array
for (let [key, value] of entriesArray) {
  console.log(key, value);
}

Output:

key1 value1
key2 value2
key3 value3

Method 6: Using the `Object.fromEntries()` method:

The Object.fromEntries() method can be used to create a new object from an iterable of key-value pairs. This iterable can be a Map object, which means that you can iterate over a Map object and create a new object from it using this method.

For example:

let myMap = new Map();

myMap.set("key1", "value1");
myMap.set("key2", "value2");
myMap.set("key3", "value3");

// Create a new object from the Map object using the Object.fromEntries() method
let entriesObject = Object.fromEntries(myMap);

// Iterate over the key-value pairs in the object
for (let key in entriesObject) {
  console.log(key, entriesObject[key]);
}