js basis of the array method

JavaScript array of power hidden in the array method.

The array to a string toString ()

JavaScript method toString () converts the array is an array of values ​​(comma delimited) string.

var fruits = ["Banana", "Orange", "Apple", "Mango"];
console.log(fruits.toString());     //Banana,Orange,Apple,Mango

All JavaScript objects have toString () method.

join () method all array elements can also be incorporated into a string.
Its behavior is similar to toString (), but you can also specify delimiters:

var fruits = ["Banana", "Orange","Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.join(" * "); 
//结果
Banana * Orange * Apple * Mango

Popping 和 Pushing

In dealing with the array, remove elements and add new elements is very simple.
Popping and Pushing means:
from the array pop project, or to push an array of projects.

• pop () method removes the last element from an array:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.pop();              // 从 fruits 删除最后一个元素（"Mango"）

• pop () method returns the "ejected" values:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var x = fruits.pop();      // x 的值是 "Mango"

• push () method (at the end of the array) to add a new element to the array:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");       //  向 fruits 添加一个新元素
console.log(fruits);       //Banana,Orange,Apple,Mango,Kiwi

• push () method returns the length of the new array:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var x =  fruits.push("Kiwi");   //  x 的值是 5

Displacement element

Displacement and pop equivalent, but the first processing element rather than the last one.

• shift () method removes the first element of the array, and all the other elements "shift" to a lower index.

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift();            // 从 fruits 删除第一个元素 "Banana"
console.log(fruits);       //Orange,Apple,Mango,Kiwi

• It shifts () method returns the string is "shifted out" in:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift();             // 返回 "Banana"

• unshift () method (in the beginning) to add a new element to the array, and "reverse displacement" old elements:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon");    // 向 fruits 添加新元素 "Lemon"

• unshift () method returns the length of the new array.

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon");    // 返回 5

Change Element

: By using their index number to access the array element
array index (subscript) begin to 0. [0] is the first element of the array, [1] is the second, [2] is the third ...

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits[0] = "Kiwi";        // 把 fruits 的第一个元素改为 "Kiwi"

The length property provides an easy way to add a new element to an array:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits[fruits.length] = "Kiwi";          // 向 fruits 追加 "Kiwi"

Removing elements

Since JavaScript array of objects belonging to which elements you can use the JavaScript delete operator to delete:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
delete fruits[0];           // 把 fruits 中的首个元素改为 undefined

Use delete the array will leave undefined empty. Please use pop () or shift () instead.

Splicing array

splice () method can be used to add a new item to the array:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 0, "Lemon", "Kiwi");
console.log(fruits);     //Banana,Orange,Lemon,Kiwi,Apple,Mango
//第一个参数（2）定义了应添加新元素的位置（拼接）。
//第二个参数（0）定义应删除多少元素。
//其余参数（“Lemon”，“Kiwi”）定义要添加的新元素。

splice () method returns an array containing the deleted items:
var fruits = ["Banana", "Orange", "Apple", "Mango"]; fruits.splice(2, 2, "Lemon", "Kiwi"); console.log(fruits); //Apple,Mango

Use splice () to remove elements

By clever parameter settings, you can use the splice () Removes the element without leaving "holes" in the array:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(0, 1);        // 删除 fruits 中的第一个元素
console.log(fruits);     //Orange,Apple,Mango
//第一个参数（0）定义新元素应该被添加（接入）的位置。
//第二个参数（1）定义应该删除多个元素。
//其余参数被省略。没有新元素将被添加。

Combining (connecting) array concat ()

concat () method to create a new array by combining (connecting) existing array:

var myGirls = ["Cecilie", "Lone"];
var myBoys = ["Emil", "Tobias", "Linus"];
var myChildren = myGirls.concat(myBoys);   // 连接 myGirls 和 myBoys
console.log(myChildren);        //Cecilie,Lone,Emil,Tobias,Linus

concat () method does not change the existing array. It always returns a new array.
concat () method can be used any number of array parameters:

//合并3个数组
var arr1 = ["Cecilie", "Lone"];
var arr2 = ["Emil", "Tobias", "Linus"];
var arr3 = ["Robin", "Morgan"];
var myChildren = arr1.concat(arr2, arr3);   // 将arr1、arr2 与 arr3 连接在一起

concat () method may be used as the parameter value:

//将数组与值合并
var arr1 = ["Cecilie", "Lone"];
var myChildren = arr1.concat(["Emil", "Tobias", "Linus"]); 

Crop array

slice () method of cutting out a segment with a new array of the array.
The present embodiment from the array element 1 ( "Orange") starts cutting a section of the array:

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(1);     //Orange,Lemon,Apple,Mango

slice () method creates a new array. It does not remove any elements from the source array.
The present embodiment from the array element 3 ( "Apple") starts cutting a section of the array:

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(3);     //Apple,Mango

slice () two acceptable parameters, such as (1, 3).
This method starts from an element selected parameters, until the end of the parameter (not included) so far.

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(1, 3);     //Orange,Lemon