Android解析json数组对象的方法及Apply和数组的三个技巧

import org.json.JSONArray; 
import org.json.JSONObject; 
//jsonData的数据格式：[{ "id": "27JpL~jd99w9nM01c000qc", "version": "abc" },{ "id": "27JpL~j6UGE0LX00s001AH", "version": "bbc" },{ "id": "27JpL~j7YkM0LX01c000gt", "version": "Wa_" }] 
JSONArray arr = new JSONArray(jsonData); 
for (int i = 0; i < arr.length(); i++) { 
JSONObject temp = (JSONObject) arr.get(i); 
String id = temp.getString("id"); 
String id = temp.getString("version"); 
}

func.apply(thisValue, [arg1, arg2, ...]) 

func(arg1, arg2, ...) 

> Math.max.apply(null, [10, -1, 5])
10

>Math.max(1,null) //相当于Math.max(1,0)
1
>Math.max(1,undefinded) //相当于Math.max(1,NaN)
NaN
>Math.max(0,-0) //正零比负零大,和==不同
0
>Math.max(-0,-1) //负零比-1大
-0 

> ["a",,"b"].forEach(function (x) { console.log(x) })
a
b
> ["a",undefined,"b"].forEach(function (x) { console.log(x) })
a
undefined
b

>for (i in ["a", "b"]) { console.log(typeof i) //数组的索引实际上是个字符串 }"string""string">["a", "b"].forEach(function (x, i) { 
console.log(typeof i) //这里的i实际上不是索引,只是个数字类型的累加器 })"number""number" 

> 1 in ["a",,"b"]
false
> 1 in ["a", undefined, "b"]
true 

> ["a",,"b"][1]
undefined
> ["a", undefined, "b"][1]
undefined 

> Array.apply(null, ["a",,"b"])
[ 'a', undefined, 'b' ]

> function returnArgs() { return [].slice.call(arguments) }
> returnArgs.apply(null, ["a",,"b"])
[ 'a', undefined, 'b' ] 

> Array.apply(null, [ 3 ])
[ , , ]

function fillHoles(arr) {
var result = [];
for(var i=0; i < arr.length; i++) {
result[i] = arr[i];
}
return result;
} 

> fillHoles(["a",,"b"])
[ 'a', undefined, 'b' ] 

> _.compact(["a",,"b"])
[ 'a', 'b' ]
> _.compact(["a", undefined, "b"])
[ 'a', 'b' ]
> _.compact(["a", false, "b"])
[ 'a', 'b' ] 

> Array.prototype.concat.apply([], [["a"], ["b"]])
[ 'a', 'b' ] 

> Array.prototype.concat.apply([], [["a"], "b"])
[ 'a', 'b' ]

> Array.prototype.concat.apply([], [[["a"]], ["b"]])
[ [ 'a' ], 'b' ]

> _.flatten([[["a"]], ["b"]])
[ 'a', 'b' ]