Google API and Google Drive JavaScript helpers. See my blog post for more information. http://joshmonson.com/blog/2013/06/27/google-drive/

GoogleAPILoader.js

var GoogleAPILoader = (function() {
    "use strict";

    function GoogleAPILoader(config) {
        this.clientId = config.clientId;
        this.apiKey = config.apiKey;
        this.scopes = config.scopes;
        this.clientLibraries = config.clientLibraries || [];
    }

    /**
     * Step 1: Load the library
     * @param callback {Function}
     */
    function loadLibrary(callback) {
        $.getScript("https://apis.google.com/js/client.js", function () {
            // Keep checking until the library is loaded
            (function checkIfLoaded() {
                if (gapi.client)
                    callback();
                else
                    window.setTimeout(checkIfLoaded, 10);
            })();
        });
    }

    /**
     * Step 2: Set the API key
     */
    function setApiKey() {
        gapi.client.setApiKey(this.apiKey);
    }

    /**
     * Step 3: Load the client libraries
     * @param callback {Function}
     */
    function loadClientLibraries(callback) {
        // Asynchronously load all the libraries
        var count = 0,
            _this = this;
        this.clientLibraries.forEach(function(library) {
            gapi.client.load(library.name, library.version, function () {
                if (++count === _this.clientLibraries.length) {
                    callback();
                }
            });
        });

        // Move on if there are no library to load
        if (!this.clientLibraries || !this.clientLibraries.length) {
            callback();
        }
    }

    GoogleAPILoader.prototype.load = function (callback) {
        var _this = this;
        loadLibrary(function () {
            setApiKey.call(_this);
            loadClientLibraries.call(_this, callback);
        });
    };

    /**
     * Step 4a: Get authorization from the user.
     * @param success {Function} A success callback
     * @param error {Function} A error/access denied callback
     */
    GoogleAPILoader.prototype.renewAuthorization = function (success, error) {
        // Try to get authorization without a popup.
        var params = {
            client_id: this.clientId,
            scope: this.scopes,
            immediate: true
        };
        gapi.auth.authorize(params, function(authResult) {

            // Check the results
            if (authResult && !authResult.error) {
                success && success();
            } else {
                error && error();
            }
        });
    };

    /**
     * Step 4b: Get explicit authorization from the user.
     * @param success {Function} A success callback
     * @param error {Function} A error/access denied callback
     */
    GoogleAPILoader.prototype.getAuthorization = function (success, error) {
        // Get authorization from a popup.
        var params = {
            client_id: this.clientId,
            scope: this.scopes,
            immediate: false
        };
        gapi.auth.authorize(params, function(authResult) {

            // Check the results
            if (authResult && !authResult.error) {
                success && success();
            } else {
                error && error();
            }
        });
    };

    return GoogleAPILoader;
})();

GoogleDriveFileUploader.js

var GoogleDriveFileUploader = (function() {
    "use strict";

    function uploadMultipart(body, boundary, callback) {
        var request = gapi.client.request({
            'path': '/upload/drive/v2/files',
            'method': 'POST',
            'params': {'uploadType': 'multipart'},
            'headers': {
                'Content-Type': 'multipart/mixed; boundary="' + boundary + '"'
            },
            'body': body});
        if (!callback) {
            callback = function(file) {
                console.log(file)
            };
        }
        request.execute(callback);
    }

    function generateMultipartData(data, metadata) {
        var boundary = '-------314159265358979323846';
        var delimiter = "\r\n--" + boundary + "\r\n";
        var close_delim = "\r\n--" + boundary + "--";

        var base64Data = btoa(data);
        var body = delimiter +
            'Content-Type: application/json\r\n\r\n' +
            JSON.stringify(metadata) +
            delimiter +
            'Content-Type: ' + metadata.mimeType + '\r\n' +
            'Content-Transfer-Encoding: base64\r\n' +
            '\r\n' +
            base64Data +
            close_delim;

        return {
            body: body,
            boundary: boundary
        };
    }

    return {
        uploadFile: function (file, metadata, callback) {
            var reader = new FileReader();
            reader.readAsBinaryString(file);
            reader.onload = function() {
                // Generate the multipart data (body and boundary)
                var data = generateMultipartData(reader.result, metadata);

                // Upload the file
                uploadMultipart(data.body, data.boundary, callback);
            };
        },
        uploadString: function (string, metadata, callback) {
            // Generate the multipart data (body and boundary)
            var data = generateMultipartData(string, metadata);

            // Upload the string
            uploadMultipart(data.body, data.boundary, callback);
        }
    };
})();