将两个有序数组合并为一个有序数组

function sortSTB(arr1,arr2){
    let index1 = 0,index2 = 0;
    let result = [];
    while(index1 !== arr1.length && index2 !== arr2.length){
        if(arr1[index1] <= arr2[index2]){
            result.push(arr1[index1]);
            index1++;
        }else{
            result.push(arr2[index2]);
            index2++;
        }
    }
    if(index1 === arr1.length){
        result = result.concat(arr2.slice(index2));
    }else{
        result = result.concat(arr1.slice(index1));
    }

    return result;
}