Master the Deno JavaScript Runtime/

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Deno Web APIs

Deno Web APIs

Explore and test some Web APIs supported by Deno to achieve some common tasks.

We'll cover the following...

This lesson takes inspiration from an article written by Luca Casonato on Deno’s blog (see the Appendix: Further Resources for the link). Here we’ll learn some useful Deno APIs (only a small subset). Each of them, provide us a code widget to experiment with these APIs directly.

Encoding/Decoding (base64)

We can encode/decode base64 strings with the atob and btoa functions.

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const encoded = btoa("Learnind Deno is really fun!");
console.log("encoded: ", encoded );
const decoded = atob(encoded);
console.log("decoded: ", decoded );

Encoding/Decoding (binary)

Similar to the previous two functions, we can also decode/encode strings from and into a binary representation (Uint8Array). This is possible with the TextEncoder and TextDecoder APIs.

const stringToEncode = "Let's encode something with Deno!";

const textEncoder = new TextEncoder();
const encodedBytes = textEncoder.encode(stringToEncode);
console.log("Encoded bytes: ", encodedBytes);

const textDecoder = new TextDecoder();
const plainText = textDecoder.decode(encodedBytes);
console.log("Decoded bytes into string: ", plainText);
Encoding and decoding (binary) functions

Cryptography functions

With version 1.18, Deno completely implements the Web Cryptography API. It is a standard JS API for performing cryptographic tasks like hashing, encryption, and decryption.

const uuid = crypto.randomUUID();
console.log('Generated new UUID: ', uuid);
console.log('\n---------------------------------------------------------------')


const bytes = await crypto.getRandomValues(new Uint8Array(16));
console.log('Array with random integers: ', bytes);
console.log('\n---------------------------------------------------------------');

const privateKey = await crypto.subtle.generateKey(
    { name: "HMAC", "hash": "SHA-256" }, // Target algorithm
    true,                                // Is Extractable 
    ["sign", "verify"]                   // Allowed usages
);
console.log('Our secret key: ', privateKey);


const exportedKey = await crypto.subtle.exportKey(
    "raw",
    privateKey
);

// Export the generated key as `ArrayBuffer`
const exportedKeyBuffer = new Uint8Array(exportedKey);

const keyAsString = String.fromCharCode.apply(null, exportedKeyBuffer as any);
// You can use the 'btoa' function explained before
const exportedBase64 = btoa(keyAsString);
const pem = `
-----BEGIN PRIVATE KEY-----
${exportedBase64}
-----END PRIVATE KEY-----`;

console.log('Exported PEM Key: ', pem);
Cryptography functions

  • Line 1: The method crypto.randomUUID() allows us to generate a random UUID. This can be a convenient way to generate unique IDs for our objects.

  • Line 6: The method crypto.randomUUID() ...