index.js

var dbdiff = require("dbdiff");

module.exports = function (Sequelize, diffOptions) {
  diffOptions = diffOptions || { level: "drop" };
  if (Sequelize.prototype.syncDiff) return;

  var sequelizeMethods = ["define"];
  var modelMethods = ["belongsTo", "hasOne", "hasMany", "belongsToMany"];

  sequelizeMethods.forEach(function (name) {
    var func = Sequelize.prototype[name];
    Sequelize.prototype[name] = function () {
      var args = Array.prototype.slice.call(arguments);
      this.diff_actions = this.diff_actions || [];
      this.diff_actions.push({ method: name, args: args });
      return func.apply(this, args);
    };
  });

  modelMethods.forEach(function (name) {
    var func = Sequelize.Model.prototype[name];
    Sequelize.Model.prototype[name] = function () {
      var args = Array.prototype.slice.call(arguments);
      var sequelize = this.sequelize;
      sequelize.diff_actions = sequelize.diff_actions || [];
      sequelize.diff_actions.push({
        method: name,
        args: args,
        model: this.name,
      });
      return func.apply(this, args);
    };
  });

  Sequelize.prototype.syncDiff = function (options) {
    var self = this;
    const allOptions = { ...this.options, database: options.database };
    var sequelize = new Sequelize(
      options.database,
      options.username,
      options.password,
      allOptions
    );
    this.diff_actions.forEach(function (action) {
      if (!action.model) {
        sequelize[action.method].apply(sequelize, action.args);
      } else {
        var model = sequelize.model(action.model);
        action.args[0] = sequelize.model(action.args[0].name);
        model[action.method].apply(model, action.args);
      }
    });

    var selfOptions = {
      dialect: self.options.dialect,
      username: self.config.username,
      password: self.config.password,
      database: self.config.database,
      port: self.config.port,
      host: self.config.host,
      dialectOptions: self.config.dialectOptions,
    };
    var diff = new dbdiff.DbDiff();
    return sequelize
      .sync({ force: true })
      .then(function () {
        return diff.compare(selfOptions, {
          ...selfOptions,
          database: options.database,
        });
      })
      .then(function () {
        return diff.commands(diffOptions.level);
      });
  };
};