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maps.md

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A map data structure allows you to store key - value pairs. Keys can be of any data type.

Maps are created using new Map()

const myMap = new Map();

Maps Methods

  1. set(key, value) - adds a key value pair to the map or updates if the key-value pair already exists.
const student = new Map();
student.set("name", "Gideon  Mwangi");
student.set("grade", "A");
student.set("position", 1);
student.set("courses", ["Web Dev", "software Engineering"]);

console.log(student)
output:
Map(4) {
'name' => 'Gideon  Mwangi',
'grade' => 'A',
'position' => 1,
'courses' => [ 'Web Dev', 'software Engineering' ]
}
  1. get(key) - returns the value associated with the specific key in the map or undefined if it doesn't exist.
const student = new Map();
student.set("name", "Gideon  Mwangi");
student.set("grade", "A");
student.set("position", 1);
student.set("courses", ["Web Dev", "software Engineering"]);

console.log(student.get("name"));
console.log(student.get("subjects"));// its not defined
output:
Gideon  Mwangi
undefined
  1. has(key) - returns true if the map contains the specified key. false otherwise.
const student = new Map();
student.set("name", "Gideon  Mwangi");
student.set("grade", "A");
student.set("position", 1);
student.set("courses", ["Web Dev", "software Engineering"]);

console.log(student.has("name"));
console.log(student.has("subjects"));
output:
true
false
  1. delete(key) - removes a specified key-value air from the map.
const student = new Map();
student.set("name", "Gideon  Mwangi");
student.set("grade", "A");
student.set("position", 1);
student.set("courses", ["Web Dev", "software Engineering"]);

student.delete("grade");
student.delete("position");

console.log(student);
output:
Map(2) {
'name' => 'Gideon  Mwangi',
'courses' => [ 'Web Dev', 'software Engineering' ]
}
  1. size - returns the number of key-value pairs in a map.
const student = new Map();
student.set("name", "Gideon  Mwangi");
student.set("grade", "A");
student.set("position", 1);
student.set("courses", ["Web Dev", "software Engineering"]);

console.log(student.size);
output:
4
  1. clear() - removes all the key-value pairs from a map.
const student = new Map();
student.set("name", "Gideon  Mwangi");
student.set("grade", "A");
student.set("position", 1);
student.set("courses", ["Web Dev", "software Engineering"]);

student.clear();
console.log(student);
output:
Map(0) {}