有序数组对应无序数组

let arr =['A', 'U', 'B', 'R', 'S'];

let U = [];

let A = [];

let S = [];

for (let i=0;i<arr.length;i++){

switch (arr[i]){

    case 'U':

    U.push(arr[i]);

    break;

case 'A':

  A.push(arr[i]);

  break;

case 'S':

  S.push(arr[i]);

  break;

}

}

let newArr = U.concat(A).concat(S);

console.log(newArr)

//['U','A','S']