split_array: function(arr, len) {
    console.log(arr);
    let index = 0;
    var result = [];
    let res = [];
    let arr_index = 0;
    let arr_index_j = 0;
    let arr_i = 0;
    let arr_a = [];
    for (let o in arr) {
        index ++;
    }
    for (var i = 0; i < index; i += len) {
        let arr_i = 0; //記錄每個小陣列的下標
        let arr_a = []; //記錄每個小陣列
        for (let j = i * len; j < (len + i * len); j++) {
            if (arr[arr_index_j]) {
                arr_a.push(arr[arr_index_j]); //向每個小陣列內新增元素
                arr_index_j++;
                arr_i = arr_i++;
            }
        }
        arr_index++;
        result.push(arr_a);
    }
    return result;
}