var gulp = require("gulp");
var rev = require("gulp-rev");                    //用哈希码来修改引用文件名
var revReplace = require("gulp-rev-replace");     //更新引用文件名
var useref = require("gulp-useref");              //注释性文字来告诉gulp要怎样操作,一般是合并打包文件
var filter = require("gulp-filter");              //从水流中筛选出来一些水，处理完再放回水流中
var uglify = require("gulp-uglify");              //压缩js
var csso = require("gulp-csso");                  //压缩css

gulp.task("default",function() {
    var jsFilter = filter("**/*.js",{restore:true});
    var cssFilter = filter("**/*.css",{restore:true});
    var indexHtmlFilter = filter(["**/*","!**/index.html"],{restore:true});

    return gulp.src("src/index.html")
           .pipe(useref())
           // .pipe(jsFilter())
           // .pipe(uglify())              // Minify any javascript sources
           .pipe(jsFilter.restore)
           .pipe(cssFilter)
           .pipe(csso())               // Minify any CSS sources
           .pipe(cssFilter.restore)
           .pipe(indexHtmlFilter)
           .pipe(rev())                // Rename the concatenated files
           .pipe(indexHtmlFilter.restore)
           .pipe(revReplace())         // Substitute in new filenames
           .pipe(gulp.dest("dist"));
});

**************************************************
下面是修改的部分，修改完可以合并js，但是并没有压缩
return gulp.src("src/index.html")
           .pipe(useref())
           // .pipe(jsFilter())
           // .pipe(uglify())              // Minify any javascript sources
           .pipe(jsFilter.restore)
           .pipe(cssFilter)
           .pipe(csso())               // Minify any CSS sources
           .pipe(cssFilter.restore)
           .pipe(indexHtmlFilter)
           .pipe(rev())                // Rename the concatenated files
           .pipe(indexHtmlFilter.restore)
           .pipe(revReplace())         // Substitute in new filenames
           .pipe(gulp.dest("dist"));

如果不注释这两行，就会报错

// .pipe(jsFilter())
 // .pipe(uglify())

TypeError: jsFilter is not a function

请问一下老师这是什么原因？