What Is Map Data Structure?


Heather Bennett

The map data structure is a fundamental concept in computer science and programming. It is a collection of key-value pairs where each key is unique and associated with a value. It is also known as an associative array, dictionary, or hash table.

What Is a Key-Value Pair?

In a map data structure, the key represents the identifier or label for a particular value. The value, on the other hand, can be any data type such as numbers, strings, objects, or even other maps. The key-value pairs are stored together and can be accessed using their respective keys.

Why Use Map Data Structure?

The map data structure provides an efficient way to store and retrieve data by using keys. It allows for fast lookup times, making it ideal for applications that require quick access to specific values. Additionally, maps enable developers to organize and manipulate data in a structured manner.

Common Operations on Maps

Maps support several operations that make them versatile and powerful. Some common operations include:

  • Insertion: Adding new key-value pairs to the map.
  • Deletion: Removing existing key-value pairs from the map.
  • Lookup: Retrieving the value associated with a specific key.
  • Update: Modifying the value associated with an existing key.

Example Usage

To better understand how maps work, let’s consider an example where we use a map to store information about students:

  <script type="text/javascript">
    // Create an empty map
    let studentMap = new Map();

    // Add student information
    studentMap.set('John', { age: 20, grade: 'A' });
    studentMap.set('Emily', { age: 19, grade: 'B' });

    // Access and update values
    let johnInfo = studentMap.get('John');
    johnInfo.grade = 'A+';

    // Delete a student

    // Iterate over the map
    for (let [name, info] of studentMap) {
      console.log(name + ': ' + info.grade);

In this example, we create a map called studentMap and add two entries with the students’ names as keys and their information as values. We then access John’s information using his name as the key and update his grade. Finally, we delete Emily’s entry from the map and iterate over the remaining entries to display each student’s name and grade.


The map data structure is a powerful tool for organizing and manipulating data in programming. Its key-value pair nature allows for efficient lookup operations and flexible data storage. By understanding how to use maps effectively, you can enhance your programming skills and build more robust applications.

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