每日一题：类数组转数组有几种方式？

    var obj = {
        0:'a',
        1:'b',
        length:2
    }
    console.log(Array.from(obj)) //['a','b']
    console.log(Array.prototype.slice.call(obj))//['a','b']
    console.log([].slice.call(obj))//['a','b']