FileUploadtoSP.js

function uploadFile(listName, id, file) {
        var deferred = $.Deferred();
        var fileName = file.name;
	getFileBuffer(file).then(
            function (buffer) {
                var bytes = new Uint8Array(buffer);
                var binary = '';
                for (var b = 0; b < bytes.length; b++) {
                    binary += String.fromCharCode(bytes[b]);
                }
                var scriptbase = _spPageContextInfo.webServerRelativeUrl + "/_layouts/15/";
                console.log(' File size:' + bytes.length);
                $.getScript(scriptbase + "SP.RequestExecutor.js", function () {
                    var createitem = new SP.RequestExecutor(_spPageContextInfo.webServerRelativeUrl);
                    createitem.executeAsync({
                        url: _spPageContextInfo.webServerRelativeUrl + "/_api/web/lists/GetByTitle('" + listName + "')/items(" + id + ")/AttachmentFiles/add(FileName='" + file.name + "')",
                        method: "POST",
                        binaryStringRequestBody: true,
                        body: binary,
                        success: fsucc,
                        error: ferr,
                        state: "Update"
                    });
                    function fsucc(data) {
                        console.log(data + ' uploaded successfully');
                        deferred.resolve(data);
                    }
                    function ferr(data) {
                        console.log(fileName + "not uploaded error");
                        deferred.reject(data);
                    }
                });

            },
            function (err) {
                deferred.reject(err);
            }
        );
	return deferred.promise();
}
    function getFileBuffer(file) {
        var deferred = $.Deferred();
        var reader = new FileReader();
        reader.onload = function (e) {
            deferred.resolve(e.target.result);
        }
        reader.onerror = function (e) {
            deferred.reject(e.target.error);
        }
        reader.readAsArrayBuffer(file);
        return deferred.promise();
    }