The **`has()` function** of the map object accepts a key in string format and returns a boolean value of `true` if the specified key exists. Otherwise, the function returns `false`.
> **Map** is a data structure in JavaScript that allows the storage of [key, value] pairs where any value can be used as either a key or value.

# Syntax
```
mapObject.has(key)
```
The `has()` function takes a key in the​ string format. It returns a boolean value that indicates ​the presence of that key in the Map object.

# Code
The code below illustrates the use of the `has()` function in Javascript:

// creating a map object
var myMap = new Map([['a', 1], ['b', 2], ['c', 3]]);

// checking for a key that exists in the map. Should 
// return true
console.log(myMap.has('c'))

// checking for a key that does not exists in the map. 
// Should return false
console.log(myMap.has('w'))

What is Map.has() function in Javascript?

Determines if a specified key exists in a JavaScript Map object, returning true or false.