ES6数组的新增高级方法

    //filter    过滤器
    //map       映射
    //reduce    汇总

    //筛选并计算大于等于10的数并打5折，然后求和
    let goods = [30, 80, 50, 5, 3, 1, 60, 9];

    let sum = goods.filter(n => n >= 10).map(n => n*0.5).reduce((s, n)=>s+n);

    console.log(sum);