es6如何使用padStart()和padEnd()方法

    var  a1 = '123'
    console.log(a1.padStart(4,'abc'))//a123
    console.log(a1.padStart(6,'abc'))//abc123
    console.log(a1.padEnd(4,'abc'))//123a
    console.log(a1.padEnd(6,'abc'))//123abc

    var arr = [1,2,3,4,5,6]
    var newArr = [];
    for(var i = 0; i<arr.length;i++){
      newArr.push(arr[i].toString().padStart(2,0))
    }
    console.log(newArr)//(6) ["01", "02", "03", "04", "05", "06"]