why object.keys reading keys from middle of an object

I have an object

 let files = {
            '00':{},
            '01':{},
            '02':{},
            '03':{},
            '04':{},
            '05':{},
            '06':{},
            '07':{},
            '08':{},
            '09':{},
            '10':{},
            '11':{},
            '12':{},
            '13':{},
            '14':{},
            '15':{}
        }

console.log(Object.keys(files))

the result I’m getting is this. why it’s reading key from 10 not from 00?

["10","11","12","13","14","15","00","01","02","03","04","05","06","07","08","09"]

How to make it read from zero i.e first key of an object?