TypeScript Tutorials

How to Check if a Key Exists in a Map in TypeScript

How to Check if a Key Exists in a Map in TypeScript ?

Answer

To check if a key exists in a map in TypeScript, you can use the has method. This method returns a boolean value indicating whether the map contains the specified key.

✐ Examples

1 Checking if a Key Exists Using has Method

We can check if a key exists in a map in TypeScript using the has method, which returns true if the map contains the specified key and false otherwise.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the has method to check for a specific key in the map. The has method returns a boolean value indicating whether the map contains the specified key.
We print the result to the console using the console.log function.

TypeScript Program

let myMap: Map<string, number> = new Map([
    ['one', 1],
    ['two', 2],
    ['three', 3]
]);

// Check if a key exists using has method
const keyExists = myMap.has('two');

// Print the result
console.log(`Does key 'two' exist? ${keyExists}`);

Output

Does key 'two' exist? true

2 Checking if a Key Does Not Exist Using has Method

We can check if a key does not exist in a map in TypeScript using the has method, which returns false if the map does not contain the specified key.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the has method to check for a specific key in the map. The has method returns a boolean value indicating whether the map contains the specified key.
We print the result to the console using the console.log function.

TypeScript Program

let myMap: Map<string, number> = new Map([
    ['one', 1],
    ['two', 2],
    ['three', 3]
]);

// Check if a key does not exist using has method
const keyExists = myMap.has('four');

// Print the result
console.log(`Does key 'four' exist? ${keyExists}`);

Output

Does key 'four' exist? false

3 Checking Multiple Keys Using has Method

We can check if multiple keys exist in a map in TypeScript using the has method, which returns true if the map contains the specified key and false otherwise.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We use the has method to check for multiple keys in the map. The has method returns a boolean value indicating whether the map contains the specified key.
We print the results to the console using the console.log function.

TypeScript Program

let myMap: Map<string, number> = new Map([
    ['one', 1],
    ['two', 2],
    ['three', 3]
]);

// Check if multiple keys exist using has method
const keyExistsOne = myMap.has('one');
const keyExistsFour = myMap.has('four');

// Print the results
console.log(`Does key 'one' exist? ${keyExistsOne}`);
console.log(`Does key 'four' exist? ${keyExistsFour}`);

Output

Does key 'one' exist? true
Does key 'four' exist? false

Summary

In this tutorial, we learned How to Check if a Key Exists in a Map in TypeScript language with well detailed examples.

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How to Check if a Key Exists in a Map in TypeScript