var gulp = require("gulp"),
    babel = require("gulp-babel");    // 用于ES6转化ES5
var uglify = require('gulp-uglify'); // 用于压缩 JS
const { watch } = require('gulp');

var src1 = "js/es6/*.js";  //es6目录
var src2 = "js/es5";  //es5目录

// 单次转换
gulp.task("es", function () {
  return gulp.src(src1)// ES6 源码存放的路径
  .pipe(babel()) 
    .pipe(gulp.dest(src2)); //转换成 ES5 存放的路径
});

// 压缩 js 文件
gulp.task('min', function() {
    // 1. 找到文件
    gulp.src('dist/*.js')
        // 2. 压缩文件
        .pipe(uglify())
        // 3. 另存压缩后的文件
        .pipe(gulp.dest('min/js'))
    });

// 自动监控任务
gulp.task('watch', function (r) {
    const watcher = watch([src1]);

    watcher.on('change', function(path, stats) {
        console.log(path.path)
        gulp.src(path.path)
        .pipe(babel()) 
        .pipe(gulp.dest(src2))
    });

    watcher.on('add', function(path, stats) {
        console.log('add')
    });

    watcher.on('unlink', function(path, stats) {
      console.log(`File ${path} was removed`);
    });
});