摘要：例如會(huì)刪除當(dāng)前數(shù)組位置的項(xiàng)，然后再?gòu)奈恢瞄_始插入字符串。對(duì)數(shù)組中的每一項(xiàng)運(yùn)行給定函數(shù)，返回該函數(shù)會(huì)返回的項(xiàng)組成的數(shù)組。則從數(shù)組的最后一項(xiàng)開始，向前遍歷到第一項(xiàng)。

1、隊(duì)尾插入push

   var colors = ["red","green"];
   colors.push("black"):
   console.log(colors); //["red","green","black"]

2、隊(duì)尾刪除并返回刪除的最后一項(xiàng)pop

   var colors = ["red","green","black"];
   var item = colors.pop();
   console.log(item); //"black"

3、隊(duì)首插入unshift()

   var colors = ["red","green"];
   colors.unshift("black");
   var item = colors.pop();
   console.log(item); //"black"

4、隊(duì)首刪除shift()

   var colors = ["red","green","black"];
   colors.shift();
   console.log(colors); //["green","black"]

5、數(shù)組一添加數(shù)組二concat()

   var colors = ["red","green","black"];
   var colors2 = colors.concat("yellow",["blue","brown"]);
   console.log(colors); //["red","green","black"]
   console.log(colors2); //["red","green","black","yellow","blue","brown"]

6、數(shù)組的截取slice()
只傳一個(gè)參數(shù)：從數(shù)組這個(gè)參數(shù)的下標(biāo)開始截取一直到數(shù)組結(jié)束。

   var colors = ["red","green","black"];
   colors.slice(1); //["green","black"]
   console.log(colors); //["red","green","black"]

傳兩個(gè)參數(shù)：第一個(gè)是截取開始的位置，第二個(gè)是截取結(jié)束的位置

   var colors = ["red","green","black","yellow","blue","brown"];
   colors.slice(1,3)//從位置1開始，到位置2結(jié)束["green","black"];

7、數(shù)組的splice()方法

   有三種用法：

刪除：可以刪除任意數(shù)量的項(xiàng)，只需指定兩個(gè)參數(shù)：第一個(gè)參數(shù)為刪除開始的位置，第二個(gè)參數(shù)為刪除項(xiàng)數(shù)。

插入：可以向指定位置插入任意數(shù)量的項(xiàng)，只需提供3個(gè)參數(shù)：起始位置、0（要?jiǎng)h除的項(xiàng)數(shù)）和要插入的項(xiàng)。例如：splice（2,0,"red","green")，會(huì)從當(dāng)前數(shù)組的位置2開始插入字符串"red"和"green"。

替換: 可以向指定位置插入任意數(shù)量的項(xiàng)，且同事刪除任意數(shù)量的項(xiàng)，只需提供3個(gè)參數(shù)：起始位置、要?jiǎng)h除的項(xiàng)數(shù)和要插入的任意數(shù)量的項(xiàng)。插入的項(xiàng)數(shù)不必與刪除項(xiàng)數(shù)相等。例如：splice (2,1,"red","green") 會(huì)刪除當(dāng)前數(shù)組位置2的項(xiàng)，然后再?gòu)奈恢?開始插入字符串。

   var colors = ["red","green","black"];
   var removed = colors.splice(0,1);
   console.log(colors); //["green","black"]
   console.log(removed); //["red"]
    
   removed = colors.splice(1,0,"yellow","orange");
   console.log(colors); //["green","yellow","orange","black"]
   console.log(removed); //[]

   removed = colors.splice(1,1,"red","purple");
   console.log(colors); //["green","red","purple","orange","black"]
   console.log(removed); //["yellow"]

8、位置方法indexOf()和lastIndexOf()

indexOf()和lastIndexOf()都接收兩個(gè)參數(shù)，第一個(gè)參數(shù)是要查找的項(xiàng)，第二個(gè)（可選）查找開始的位置，indexOf()是從數(shù)組頭開始查，lastIndexOf()是從數(shù)組尾開始查找。

   var numbers = [1,2,3,4,5,4,3,2,1];

   console.log(numbers.indexOf(4)); //3
   console.log(numbers.lastIndexOf(4)); //5
   
   console.log(numbers.indexOf(4,4)); //5
   
   var person = {name: "vivi"};
   var people = [{name: "vivi"}];
   
   var morePeople = [person];
   console.log(people.indexOf(person)); //-1
   console.log(morePeople.indexOf(person)); //0

9、查找find()方法
查找符合條件的第一項(xiàng)

   var inventory = [
    {name: "apples", quantity: 2},
    {name: "bananas", quantity: 0},
    {name: "cherries", quantity: 5}
   ];
   const inventorItem = inventory.find((item) => item.name === "apples");
   console.log(inventorItem); //{name: "apples", quantity: 2}

10、迭代方法
傳入這些方法中的函數(shù)會(huì)接收三個(gè)參數(shù)：數(shù)組項(xiàng)的值、該項(xiàng)在數(shù)組中的位置和數(shù)組對(duì)象本身。

every(): 對(duì)數(shù)組中的每一項(xiàng)運(yùn)行給定函數(shù)，如果該函數(shù)對(duì)每一項(xiàng)都返回true，則返回true。

filter(): 對(duì)數(shù)組中的每一項(xiàng)運(yùn)行給定函數(shù)，返回該函數(shù)會(huì)返回true的項(xiàng)組成的數(shù)組。

forEach(): 對(duì)數(shù)組中的每一項(xiàng)運(yùn)行給定函數(shù)，這個(gè)方法沒(méi)有返回值。

map(): 對(duì)數(shù)組中的每一項(xiàng)運(yùn)行給定函數(shù)，返回每次函數(shù)調(diào)用的結(jié)果組成的數(shù)組。

some(): 對(duì)數(shù)組中的每一項(xiàng)運(yùn)行給定函數(shù)，如果該函數(shù)對(duì)任一項(xiàng)返回true，則返回true。

   var numbers = [1,2,3,4,5,4,3,2,1];
   var everyResult = numbers.every((item, index, array) => {
        return item > 2;
   });
   console.log(everyResult); //false
   
   var someResult = numbers.some((item, index, array) => {
       return  item > 2;
   });
   console.log(someResult); //true

  var numbers = [1,2,3,4,5,4,3,2,1];
  var filterResult = numbers.filter((item, index, array) => {
    return item > 2;
  });
  console.log(filterResult); //[3,4,5,4,3]

   var numbers = [1,2,3,4,5,4,3,2,1];
   var mapResult = numbers.map((item, index, array) => {
    return item * 2;
  });
  console.log(mapResult); //[2,4,6,8,10,8,6,4,2]

   var numbers = [1,2,3,4,5,4,3,2,1];
   numbers.forEach((item, index, array) => {
       //執(zhí)行某些操作
   });

11、歸并方法reduce()和reduceRight()

這兩個(gè)方法都會(huì)迭代數(shù)組的所有項(xiàng)，然后構(gòu)建一個(gè)最終返回的值。
reduce（）方法從數(shù)組的第一項(xiàng)開始，逐個(gè)遍歷到最后。                                  
reduceRight（）則從數(shù)組的最后一項(xiàng)開始，向前遍歷到第一項(xiàng)。

   var values = [1,2,3,4,5];
   var sum = values.reduce((prev, cur, index, array) => {
       return prev + cur;
   });
   console.log(sum); //15

   var values = [1,2,3,4,5];
   var sum = values.reduceRight((prev, cur, index, array) => 
   {
       return prev + cur;
   });
   console.log(sum); //15