前言 :
因為最近瘋狂的用 javascript 操作 JSON，發現陣列實在是超級無敵好用
不管是在陣列上的資料儲存、過濾、排序、組合都超級好用
所以有整理了一些常用 + 日後可能會用到的操作方式
完整的 Array 用法可以看 MDN 官網
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
這篇只是列出來比較常用或可能會用到的操作
讓自己日後比較方便查~
ps :
有些操作方法是定義在 ECMAScript 5 中
如果要在很舊的瀏覽器中使用可以自行定義在 Array.prototype 裡面
join : 將陣列元素用固定符號串成字串 (常用)
var arr = ["jack", "john", "may", "su", "Ada"];
var str = arr.join("、");
ANS：
str 為 jack、john、may、su、Ada
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/join
清除或增加陣列長度 (清除陣列很好用)
var arr = [1, 2, 3, 4, 5, 6];
arr.length = 2;
ANS：
[1,2]
arr.length = 0;
ANS：
[]
arr.length = 5;
ANS：
[,,,,]
刪除陣列元素
var arr = [1, 2, 3, 4, 5, 6];
delete arr[1];
ANS：
[1,,3, 4, 5, 6]
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete
Array.form : 將字串或輸入參數組成陣列 (非常方便)
MDN 範例 :
Array-like object (arguments) to Array
(function () {
var args = Array.from(arguments);
return args;
})(1, 2, 3);
ANS：
[1, 2, 3]
Any iterable object...
Array.from(new Set(["foo", window]));
ANS：
["foo", window]
Map
var m = new Map([[1, 2], [2, 4], [4, 8]]);
Array.from(m);
ANS：
[[1, 2], [2, 4], [4, 8]]
Strings are both array-like and iterable
Array.from("foo"); //<-- 超方便
ANS：
["f", "o", "o"]
Using an arrow function as the map function to
manipulate the elements
Array.from([1, 2, 3], x => x + x);
ANS：
[2, 4, 6]
Generate a sequence of numbers
Array.from({length:5}, (v, k) => k);
ANS：
[0, 1, 2, 3, 4]
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from
sort : 陣列排序 (很好用)
var arr = [5, 9, 1, 3, 2, 6];
arr.sort();
ANS：
[1,2,3,5,6,9]
//也可以這樣寫
arr.sort(function (a,b) {
return a - b;
})
ANS：
[1,2,3,5,6,9]
//如果要反過來排序的話
arr.sort(function (a,b) {
return b - a;
})
ANS：
[9,6,5,3,2,1]
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort
push : 新增元素或元素組到陣列 (想不用到都不行)
var arr = {
name: [],
data:[]
};
arr.name.push("jack");
arr.name.push("john");
arr.data.push({ weight: 60, height: 170 });
arr.data.push({ weight: 62, height: 175 });
JSON.stringify(arr);
ANS：
(透過JSON.stringify 返回的是字串喔，方便看結構所以用物件實字來表示)
{
"name":["jack","john"],
"data":[
{"weight":60,"height":170},
{"weight":62,"height":175}
]
}
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push
splice : 改變陣列內容，移除或新增元素
array.splice(index , howMany[, element1[, ...[, elementN]]])
參數
index : 要從哪個索引位置開始改變
howMany : 用來指出要移除多少個元素. 如果 howMany 等於 0，則沒有任何元素被移除
element1, ..., elementN : 要加入陣列的元素，如果省略則表示不加入只刪除
官網範例 :
var myFish = ["angel", "clown", "mandarin", "surgeon"];
//removes 0 elements from index 2, and inserts "drum"
var removed = myFish.splice(2, 0, "drum");
//myFish is ["angel", "clown", "drum", "mandarin", "surgeon"]
//removed is [], no elements removed
//removes 1 element from index 3
removed = myFish.splice(3, 1);
//myFish is ["angel", "clown", "drum", "surgeon"]
//removed is ["mandarin"]
//removes 1 element from index 2, and inserts "trumpet"
removed = myFish.splice(2, 1, "trumpet");
//myFish is ["angel", "clown", "trumpet", "surgeon"]
//removed is ["drum"]
//removes 2 elements from index 0, and inserts "parrot", "anemone" and "blue"
removed = myFish.splice(0, 2, "parrot", "anemone", "blue");
//myFish is ["parrot", "anemone", "blue", "trumpet", "surgeon"]
//removed is ["angel", "clown"]
//removes 2 elements from index 3
removed = myFish.splice(3, Number.MAX_VALUE);
//myFish is ["parrot", "anemone", "blue"]
//removed is ["trumpet", "surgeon"]
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
concat : 會將兩個陣列合併產生新的陣列，原陣列不改變 (不常用，但很簡單就記一下吧)
var alpha = ["a", "b", "c"];
var numeric = [1, 2, 3];
var alphaNumeric = alpha.concat(numeric);
ANS：
["a", "b", "c", 1, 2, 3]
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat
some : 陣列比對，只要有一個元素是 true，就返回 true (很好用)
var arr = ["jack", "john", "may", "su", "Ada"];
var flag = arr.some(function (value, index, array) {
return value == "may" ? true : false;
});
ANS：
flag 為 true
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/some
every : 陣列比對，所有元素都是 true 才是 true (很好用)
var arr = ["jack", "john", "may", "su", "Ada"];
var flag = arr.every(function (value, index, array) {
return value.length > 2;
});
ANS：
flag 為 false
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/every
filter : 陣列過濾，透過 filter 的過濾條件返回一個新陣列 (非常好用)
var arr = ["jack", "john", "may", "su", "Ada"];
var arr2 = arr.filter(function (value) {
return value.length > 3;
});
arr2.join("、");
ANS：
jack、john
map : 對陣列中的各元素進行操作，操作後的值會被寫入新的陣列中並返回
var arr = [1, 2, 3, 4, 5, 6];
var arr2 = arr.map(function (element,index,array) {
return element * 2;
});
arr2.join("、");
ANS：
2、4、6、8、10、12
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map
reduce : 陣列中的每一個元素都會呼叫一次callback函數，唯一不同的是，函數的回傳值會當作下一次呼叫的傳入值，方向為索引 0 到 陣列尾端 (冷門，幾乎可以不用記)
var arr = [1, 2, 3, 4, 5, 6];
var flag = arr.reduce(function (previousValue, currentValue, index, array) {
return previousValue + currentValue;
})
ANS：
所以 flag 為 1 + 2 + 3 + 4 + 5 + 6 = 21
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
reduceRight : 與 reduce 相同，只是是從陣列尾端到索引 0 的位置 (冷門，幾乎可以不用記)
MDN : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/ReduceRight
再來是幾個專案上有用到有關陣列的函數，都網路上人家寫好的拿來用 (有些也忘記出處)
陣列的 distinct : 取得陣列中不重複的元素值，輸出成新陣列 (有用到 jQuery)
function GetUnique(inputArray) {
var outputArray = [];
for (var i = 0; i < inputArray.length; i++) {
if ((jQuery.inArray(inputArray[i], outputArray)) == -1) {
outputArray.push(inputArray[i]);
}
}
return outputArray;
}
移除陣列中，指定的元素值之項目 (我都看不懂我在寫什麼)
出處 : Remove item from array by value
Array.prototype.remove = function () {
var what, a = arguments, L = a.length, ax;
while (L && this.length) {
what = a[--L];
while ((ax = this.indexOf(what)) !== -1) {
this.splice(ax, 1);
}
}
return this;
};
使用例子：
var ary = ['three', 'seven', 'eleven'];
ary.remove('seven');
ANS：
three,eleven
要注意的是這個方法是附加在 Array 的原型當中
所以你用下面這樣去跑，後面會多一個 remove
var content = "";
for (var key in ary) {
content += key + "\n";
}
如果不想定義在prototype，也可以把它寫成 function
function removeA(arr) {
var what, a = arguments, L = a.length, ax;
while (L > 1 && arr.length) {
what = a[--L];
while ((ax= arr.indexOf(what)) !== -1) {
arr.splice(ax, 1);
}
}
return arr;
}
var ary = ['three', 'seven', 'eleven'];
removeA(ary, 'seven');
ANS：
three,eleven
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