合并两个有序数组

function mergeArray(arr1,arr2){
    let arr = []
    while(arr1.length && arr2.length){
        if(arr1[0] > arr2[0]){
            arr = arr.concat(arr2.splice(0,1))
        }else if(arr1[0] == arr2[0]){
            arr = arr.concat(arr1.splice(0,1))
            arr = arr.concat(arr2.splice(0,1))
        }else{
            arr = arr.concat(arr1.splice(0,1))
        }
    }
    let _arr = arr1.length ? arr1 : arr2
    arr = arr.concat(_arr)
    return arr
}

function merge(arr1 = [2,3,4,5,7],arr2 = [3,5,6,7,9,10]){
    let res = []
    while(arr1.length && arr2.length){
        if(arr1[0] > arr2[0]){
            res.push(arr2.shift())
        }else if(arr1[0] < arr2[0]){
            res.push(arr1.shift())
        }else{
            res.push(arr1.shift())
            res.push(arr2.shift())
        }
    }
    let _arr = arr1.length ? arr1 :arr2
    res.push(..._arr)
    return res
}