Create algorithm for converting binary data to base64

Conversions/ArrayBufferToBase64.js

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+/**
+ * Converts an array of bytes to base64 encoding
+ * @param {ArrayBuffer} binaryData An ArrayBuffer which represents an array of bytes
+ * @returns {string} A string containing the base64 encoding of `binaryData`
+ */
+function bufferToBase64 (binaryData) {
+  // The base64 encoding uses the following set of characters to encode any binary data as text
+  const base64Table = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
+  // Every 3 bytes translates to 4 base64 characters, if we have less than 3 bytes we must append '=' chars as padding
+  const padding = 3 - (binaryData.byteLength % 3)
+  // Create an instance of Uint8Array, to read from the binaryData array buffer
+  const byteView = new Uint8Array(binaryData)
+  let result = ''
+
+  // Loop through all bytes in the buffer, in increments of 3 bytes
+  for (let i = 0; i < byteView.byteLength; i += 3) {
+    // Get the index for the next 4 base64 chars
+    const char1 = (byteView[i] & 252) >> 2
+    const char2 = ((byteView[i] & 3) << 4) + ((byteView[i + 1] & 240) >> 4)
+    const char3 = ((byteView[i + 1] & 15) << 2) + ((byteView[i + 2] & 192) >> 6)
+    const char4 = byteView[i + 2] & 63
+
+    result +=
+        base64Table[char1] +
+        base64Table[char2] +
+        base64Table[char3] +
+        base64Table[char4]
+  }
+
+  // Add padding '=' chars if needed
+  if (padding !== 3) {
+    const paddedResult = result.slice(0, result.length - padding) + '='.repeat(padding)
+    return paddedResult
+  }
+
+  return result
+}
+
+export { bufferToBase64 }

Conversions/test/ArrayBufferToBase64.test.js

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+import { bufferToBase64 } from '../ArrayBufferToBase64'
+import { TextEncoder } from 'util'
+
+describe('ArrayBufferToBase64', () => {
+  it('should encode "Hello, world!" as "SGVsbG8sIHdvcmxkIQ=="', () => {
+    const testString = 'Hello, world!'
+    const encoder = new TextEncoder()
+    const helloWorldBuffer = encoder.encode(testString)
+    const result = bufferToBase64(helloWorldBuffer)
+    expect(result).toBe('SGVsbG8sIHdvcmxkIQ==')
+  })
+
+  it('should encode binary buffer [55,23,177,234,68,26,90] as "Nxex6kQaWg=="', () => {
+    const testBuffer = new Uint8Array([55, 23, 177, 234, 68, 26, 90])
+    const result = bufferToBase64(testBuffer)
+    expect(result).toBe('Nxex6kQaWg==')
+  })
+
+  it('should encode binary buffer [0,1,2,3,4,5,6,7,8,9] as "AAECAwQFBgcICQ=="', () => {
+    const testBuffer = new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
+    const result = bufferToBase64(testBuffer)
+    expect(result).toBe('AAECAwQFBgcICQ==')
+  })
+})