js实现前面自动补全位数的方法

function PrefixInteger(num, length) { return (num/Math.pow(10,length)).toFixed(length).substr(2);}

function PrefixInteger(num, length) { return ( "0000000000000000" + num ).substr( -length );}

function PrefixInteger(num, length) { return (Array(length).join('0') + num).slice(-length);}

 let newArr= arr.map(num =>  num.toString().padStart(10, '0') ),