arrayBufferToBase64 and vice versa

arrayBufferToBase64.js

 function arrayBufferToBase64(buffer) {
        var binary = '';
        var bytes = new Uint8Array(buffer);
        var len = bytes.byteLength;
        for (var i = 0; i < len; i++) {
            binary += String.fromCharCode(bytes[i]);
        }
        return window.btoa(binary);
    }

    function base64ToArrayBuffer(base64) {
        var binary_string = window.atob(base64);
        var len = binary_string.length;
        var bytes = new Uint8Array(len);
        for (var i = 0; i < len; i++) {
            bytes[i] = binary_string.charCodeAt(i);
        }
        return bytes.buffer;
    }