箭头函数

        //es5
        var k = function (a, b) {
            return a + b;
        }
        var ttt = k(1, 2);
        console.log(k);
        console.log(ttt);

        //es6 
        var k = (a, b) => {
            return a + b;
        }
        var ttt = k(1, 2);
        console.log(k);
        console.log(ttt);