把你的任务改成函数后，简单使用；

After changing your tasks to functions, simply use;

gulp.task('default', gulp.series (watch, gulp.parallel(styles, scripts, images),

    function (done) { done(); }    
));

watch 函数将首先运行，然后是样式、脚本和图像函数并行运行.

The watch function will run first, then the styles, scripts and images functions in parallel.

来自 gulp.series 文档:

组合的嵌套深度没有强加限制使用 series() 和 parallel() 进行操作.

There are no imposed limits on the nesting depth of composed operations using series() and parallel().