JS Array類小總結

array類：

首先 ^^

陣列定義習慣上都用 ,

下面分別使用 new array() 與

，驗證時間效率**如下，看看誰用的時間少：

var a = new date ;

var arr, direct, b = ;
for(var i=0; i<10000; i++)
arr = new array();
b.push(new date() - a);
a = new date;
for(var i=0; i<10000; i++) 
direct = ;
b.push(new date() - a);
alert(b.join(" : "));

高階程式設計

1 建立 array 類物件：

（1）	

var numbers= new array();//習慣上是var numbers= ;
numbers [0] = "one";
numbers [2] = "two";
numbers [3] = "three";
numbers [35] = "four";
alert(numbers [0]);     //outputs 「one」
alert(numbers [35]);   //outputs 」four」
alert(numbers.length);  //outputs 「36」

(2)

var numbers= new array(15);// 習慣上是var numbers= [15];
alert(numbers [0]);        //outputs "undefined"
alert(numbers.length);    //outputs "15"

(3)

var numbers= new array("one","two","three");//習慣上是var numbers= ["one","two","three"];
alert(numbers [0]);      //outputs "undefined"
numbers [10] = "four";
alert(numbers.length);    //outputs "11"

(4)用字面量表示定義array物件：

var numbers= ["one","two","three"];
alert(numbers [0]);      //outputs "undefined"
numbers [10] = "four";
alert(numbers.length);     //outputs "11"

var numbers= ["one","two","three"];

alert(numbers.tostring());  //outputs "one,two,three"
alert(numbers.valueof());  //outputs "one,two,three"

3  tolocalstring()

方法。

var numbers= ["one","two","three"];

alert(numbers.tolocalestring());  //outputs "one,two,three"

4  join()

方法，，用來連線字串的值。

var numbers= ["one","two","three"];

alert(numbers.join(","));  //outputs "one,two,three"
alert(numbers.join("-and-"));  //outputs "one-and-two-and-three"
alert(numbers.join(""));  //outputs "onetwothree"
alert(numbers.join(")("));  //outputs "one)(two)(three"

方法。

var numbers= ["one","two","three"];

var arr = numbers;
var numbers2=arr.concat("four","five");
alert(numbers2.tostring());     //outputs "one,two,three,four,five"
alert(numbers.tostring());     //outputs "one,two,three"
//alert(numbers.concat("four","five"));   //outputs "one,two,three"

6  slice()

方法。

var numbers = ["one","two","three","four","five","six"];

var arr = numbers;
var numbers2 = arr.slice(1);
alert(numbers2.tostring());   //outputs "two,three,four,five,six"
var numbers3 = arr.slice(1,4);
alert(numbers3.tostring());   //outputs "two,three,four"

7 呼叫 push()

和 pop()

方法實現後進先出的結構（棧 stack

）。

var stack= ["one","two","three"];

stack.push("four");
stack.push("five","six");
alert(stack.tostring());       //outputs "two,three,four,five,six"
var removelast=stack.pop();
alert(removelast);          //outputs "six"
var removelast=stack.pop();
alert(removelast);           //outputs "five"
alert(stack.tostring());        //outputs "two,three,four"

8 呼叫 shift()

和 push()

方法實現後進後出結構（佇列 queue

）。

var queue= ["one","two","three"];

queue.push("four");
alert(queue.tostring());         //outputs "one,two,three,four"
var removefirst = queue.shift();
alert(removefirst);           //outputs "one"
alert(queue.tostring());       //outputs "two,three,four"

(1)unshift()

方法把乙個項新增在陣列的第乙個位置。

（**的上面部分可以用 8

的**）

var addfirst = queue.unshift("one");

//alert(addfirst);             //outputs "4"
alert(queue.tostring());       //outputs "one,two,three,four"

(2)reverse()

方法顛倒陣列項順序。

**銜接上面的 unshift()

。

queue.reverse(); 

alert(queue.tostring());        //outputs "four,three,two,one"

（ 3 ） sort() 方法按陣列項的公升序排列。

var queue= ["one","two","three"];

queue.sort();
alert(queue.tostring());    //outputs "one,three,two"

var queue= ["one","two","three","four","five"];

queue.splice(0,2);
alert(queue.tostring());        //outputs "three,four,five",delete one and two
queue.splice(1,1,"and1","and2","and3");
alert(queue.tostring());         //outputs "three,and1,and2,and3,four"

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