陣列 的幾種常見方法

unshift()

新增，將要給定的數值新增到陣列的開頭

var arr =

["西瓜"
,"蘋果"
,"雪梨"
,"香蕉"];
arr.
unshift
("桃子"
,"哈密瓜");
//["桃子","哈密瓜","西瓜","蘋果","雪梨","香蕉"]
console.
log(arr)
;

從陣列中刪除第乙個元素，並返回該元素的值。此方法更改陣列的長度。

從陣列中刪除的元素，如果組數為空側返回undefined

var a =[1

,2,3
];var b = a.
shift()
;console.
log(a)
;//[2,3]
console.
log(b)
;// 1

新增,將要給定的數值新增到陣列的後頭

var arr =

["西瓜"
,"蘋果"
,"雪梨"
,"香蕉"];
arr.
push
("桃子"
,"哈密瓜");
//["桃子","哈密瓜","西瓜","蘋果","雪梨","香蕉"]

從陣列中刪除最後乙個元素，並返回該元素的值。此方法更改陣列的長度。

var a =[1

,2,3
];a.pop()
;console.
log(a)
;//[1,2]

例如 arr.splice(1, 1, 「老安」,「平板」);

1.想從哪乙個後面開始新增就寫幾

var arr =

["西瓜"
,"蘋果"
,"雪梨"
,"香蕉"];
arr.
splice(1
,0,"桃子"
)//["西瓜","桃子","蘋果","雪梨","香蕉"]
arr.
splice(1
,0,"聖尼果"
,"西紅柿"
)// ["西瓜","聖尼果","西紅柿","桃子","蘋果","雪梨","香蕉"]

var arr =

["西瓜"
,"蘋果"
,"雪梨"
,"香蕉"];
arr.
splice(1
,1,"聖尼果"
,"西紅柿"
)// ["西瓜","聖尼果","西紅柿","雪梨","香蕉"]

將兩個陣列合併

var arr1 =

['a'
,'b'
,'c'];
var arr2 =
['d'
,'e'
,'f'];
//合併
console.
log(arr1.
concat
(arr2));
//["a", "b", "c", "d", "e", "f"]
//方法一
console.
log(arr1.
concat
("j"
,arr2));
//["a", "b", "c", "j", "d", "e", "f"]
console.
log(arr1.
concat
("j"
+arr2));
// ["a", "b", "c", "jd,e,f"]
//方法二
console.
log(arr1+arr2.
concat
("j"))
;//拼接在一起a,b,cd,e,f,j

將陣列（或乙個類陣列物件）的所有元素變成字串

var arr2=

["王白菜"
,"牛春"
,"野老多"];
console.
log(arr2.
join
('-'))
;//王白菜-牛春-野老多

是將陣列順序顛倒

var arr =

['one'
,'two'
,'three'];
var reversed = arr.
reverse()
; console.
log(arr)
;//["three", "two", "one"]

var arr =[1

,30,22
,49,31
,21];
arr.
sort()
;console.
log(arr)
;//[1, 21, 22, 30, 31, 49]
arr.
sort
(function
(a, b)
);

陣列的過濾

//	例子:過濾出陣列中單詞長度大於6的單詞

let words =
['spr'
,'limit'
,'like'
,'destruction'
,'present'];
let result = words.
filter
(word => word.length >6)
;console.
log(result)
//["destruction", "present"]

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