Add usage examples of the k6/experimental/webcrypto module

examples/experimental/webcrypto.js

@@ -0,0 +1,50 @@
+import { crypto } from "k6/experimental/webcrypto";
+
+export default async function () {
+  const key = await crypto.subtle.generateKey(
+    {
+      name: "AES-CBC",
+      length: 256,
+    },
+    true,
+    ["encrypt", "decrypt"]
+  );
+
+  const encoded = stringToArrayBuffer("Hello, World!");
+  const iv = crypto.getRandomValues(new Uint8Array(16));
+
+  const ciphertext = await crypto.subtle.encrypt(
+    {
+      name: "AES-CBC",
+      iv: iv,
+    },
+    key,
+    encoded
+  );
+
+  const plaintext = await crypto.subtle.decrypt(
+    {
+      name: "AES-CBC",
+      iv: iv,
+    },
+    key,
+    ciphertext,
+  );
+
+  console.log("deciphered text == original text: ", arrayBufferToHex(plaintext) === arrayBufferToHex(encoded))
+}
+
+function arrayBufferToHex(buffer) {
+  return [...new Uint8Array(buffer)]
+    .map((x) => x.toString(16).padStart(2, "0"))
+    .join("");
+}
+
+function stringToArrayBuffer(str) {
+  var buf = new ArrayBuffer(str.length * 2); // 2 bytes for each char
+  var bufView = new Uint16Array(buf);
+  for (var i = 0, strLen = str.length; i < strLen; i++) {
+    bufView[i] = str.charCodeAt(i);
+  }
+  return buf;
+}