var ary=["A","B","C","D"];
var ary2=[1,2,3,4,5,6,];
function aryJoinAry(ary,ary2) {
    var itemAry=[];
    var minLength;
    //先拿到兩個陣列中長度較短的那個陣列的長度
    if(ary.length>ary2.length){
        minLength=ary2.length;
    }
    else{
        minLength=ary.length;
    }
    //將兩個陣列中較長的陣列記錄下來
    var longAry=arguments
 
[0].length>arguments[1].length?arguments[0]:arguments[1];
    //迴圈範圍為較短的那個陣列的長度
    for (var i = 0; i < minLength; i++) {
        //將陣列放入臨時陣列中
        itemAry.push(ary[i]);
        itemAry.push(ary2[i])
    }
    //itemAry和多餘的新陣列拼接起來並返回。
    return itemAry.concat(longAry.slice(minLength));
}
console.log(aryJoinAry(ary, ary2));// ["A", 1, "B", 2, "C", 3, "D", 4, 5, 6]