REST API to get file versions

Hope you have idea how to create SharePoint App.
If you are using NAPA tool then replace below codes in APP.js file.
So i am just focusing on the REST script part to do the activities

I recommend to go through REST API for SP document libraries before proceed.

HTML file in Default.aspx 

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JS script in app.js (Paste the below methods in app.js file) Refer here
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function versionfile()  
{
    var executor;
 
    // Initialize the RequestExecutor with the app web URL.
    executor = new SP.RequestExecutor(appweburl);
 
    executor.executeAsync
    ({
 
        url: appweburl + "/_api/SP.AppContextSite(@target)/web/GetFileByServerRelativeUrl('/sites/apps/Shared Documents/RESTFolder.docx')/versions?@target='" + hostweburl + "'",
        method: "GET",
 
 
        headers:
 {
            "accept": "application/json; odata=verbose"
        },
        success: SuccessHandlerFileVersions,
        error: ErrorHandlerFileVersions
    });
}
 
/ Success Handler
    Function SuccessHandlerFileVersions (data)  
    {
        var FV;
        var jsonObject = JSON.parse(data.body);
        var results = jsonObject.d.results;
        for (var i = 0; i < results.length; i++)  
        {
            FV += results[i].VersionLabel + '\n';
        }
        / / Display the File versions
alert(FV);
}
// Error Handler
function ErrorHandlerFileVersions(data, errorCode, errorMessage)
{
    alert("Could not get the file versions: " + errorMessage);
}