SharePoint REST Api check File Is Exist or Not with file Name.

  var checkFileIsExist = function (fileName) {

                var url = "/_api/Web/lists/getByTitle('" + SharePointList.stpDoc + "')/Items?$select=FieldValuesAsText/FileRef&$expand=FieldValuesAsText&$filter=FileLeafRef eq '" + fileName + "'";

                return baseService.getRequest(url);

            };

baseService.js

    var getRequest = function (query) {

                var deferred = $q.defer();

                $http({

                    url: _spPageContextInfo.webAbsoluteUrl + query,

                    method: "GET",

                    headers: {

                        "accept": "application/json;odata=verbose",

                        "content-Type": "application/json;odata=verbose"

                    }

                }).then(function (result) {

                    deferred.resolve(result);

                }, function (result, status) {

                    deferred.reject(status);

                });

                return deferred.promise;

            };

Controller :

    stppService.checkFileIsExist("" + file.name + "").then(function (response) {

                                    if (response.data.d.results.length > 0) {

                                        alert("This file already exists, Please Rename file and upload again !!!");

                                    }