JavaScript数组降维

var arr=[
    [1,2,3,4],
    [5,6,7,8]
];

arr=String(arr).split(",");
console.log(arr);
// ["1", "2", "3", "4", "5", "6", "7", "8"]

var result=[];
for(var r=0;r<arr.length;r++){
    for(var c=0;c<arr[r].length;c++){
        result.push(arr[r][c]);
    }
}
console.log(result);
// [1, 2, 3, 4, 5, 6, 7, 8]

var result=[];
for(var r=0;r<arr.length;r++){
    result=result.concat(arr[r]);
}
console.log(result);
// [1, 2, 3, 4, 5, 6, 7, 8]

arr=Array.prototype.concat.apply([],arr)
console.log(arr);
// [1, 2, 3, 4, 5, 6, 7, 8]