1.shift()：從集合中把第一個元素刪除，並返回這個元素的值
var arr= ["a","b","c","d","e","f"];
var result= arr.shift();
console.log(arr); //["b","c","d","e","f"]
console.log(result);//a
2.unshift()：在集合開頭添加一個或更多元素，並返回新的長度
var arr= ["a","b","c","d","e","f"];
var result= arr.unshift("add");
console.log(arr); //["add","a","b","c","d","e","f"];
console.log(result);//7
3.push()：在集合中添加元素，並返回新的長度
var arr= ["a","b","c","d","e","f"];
var result= arr.push("add");
console.log(arr); //["a","b","c","d","e","f","add"];
console.log(result);//7
4.pop()：從集合中把最後一個元素刪除，並返回這個元素的值
var arr= ["a","b","c","d","e","f"];
var result= arr.pop();
console.log(arr); //["a","b","c","d","e"];
console.log(result);//f
5.splice()：splice()主要用途是向當前數組的中間插入項，可以進行刪除、插入、替換操作，然後返回被刪除的項目
array.splice(index,howmany)
- index：必需。整數，規定添加/刪除項目的位置，使用負數可從數組結尾處規定位置。
- howmany：必需。要刪除的項目數量。如果設置爲 0，則不會刪除項目
- 例子
var arr= ["a","b","c","d","e","f"];
var result= arr.splice(1,2);
console.log(arr); //["a","d","e"];
console.log(result);//["b","c"]
arrayObject.splice(index,howmany,item1,.....,itemX)
- index：必需。整數，規定添加/刪除項目的位置，使用負數可從數組結尾處規定位置。
- howmany：必需。要刪除的項目數量。如果設置爲 0，則不會刪除項目
- item1....itemx:像數組中插入的元素
- 例子:不刪除元素，添加2個元素
var arr= ["a","b","c","d","e","f"];
var result= arr.splice(1,0,"x","y");
console.log(arr); //["a","b","x","y","c","d","e","f"];
console.log(result);//[]
- 替換：替換：向指定位置插入任意數量的項同時刪除任意數量的項，插入項數和刪除項數可以不同。參數包括兩個基本參數（即刪除操作中的兩個參數類型）和要插入項的參數。（即刪除的同時添加）
- 例子:刪除1個元素，添加2個元素
var arr= ["a","b","c","d","e","f"];
var result= arr.splice(1,1,"x","y");
console.log(arr); //["a","x","y","c","d","e","f"];
console.log(result);//["b"]
6.slice()：基於當前數組中的一個或多個項創建一個新數組。
- slice()方法中可以有一個或者兩個參數(代表數組的索引值，0,1,2……)
- 當有1個參數時：返回當前數組中從此參數位置開始到當前數組末尾間所有項
- 當有2個參數時：返回當前數組中兩個參數位置間的所有項，但不返回第二個參數位置的項
- 參數也可以爲負數，表示從末尾算起，-1代表最後一個，使用方法和正數一樣。
- 例子
var arr= ["a","b","c","d","e","f"];
var result1 = arr.slice(2);
var result2= arr.slice(1,4);
var result3= arr.slice(2,-2);
var result4= arr.slice(-3,-1);
console.log(result1 ); //["c","d","e","f"];
console.log(result2 ); //["b","c","d"];
console.log(result3 );//["c","d"]
console.log(result4 );//["d","e"]
7.concat():基於當前數組中所有項創建新數組。
- 先創建數組的一個副本，若是concat()存在參數，將接收到的參數添加到副本的末尾，然後返回新構建的數組；若是沒有傳遞參數，僅僅複製當前數組並返回副本數組。
- 例子
var arr= ["a","b","c","d","e","f"];
var result= arr.concat("x","y");
console.log(arr); //["a","x","y","c","d","e","f"];
console.log(result);//["a","x","y","c","d","e","f","x","y"]
8.reverse():方法顛倒數組中元素的位置，並返回該數組的引用。
var arr= ["a","b","c","d","e","f"];
var result= arr.reverse();
console.log(arr); //["f", "e", "d", "c", "b", "a"];
console.log(result);//["f", "e", "d", "c", "b", "a"]
9.toString() 返回一個字符串，表示指定的數組及其元素。
var arr= ["a","b","c","d","e","f"];
var result= arr.toString();
console.log(arr); //["a","b","c","d","e","f"];
console.log(result);//a,b,c,d,e,f
10.forEach() 方法對數組的每個元素執行一次提供的函數。
- 爲數組中每個元素執行的函數，該函數接收三個參數
- currentValue(當前值)：數組中正在處理的當前元素；index(索引)：數組中正在處理的當前元素的索引；array：forEach()方法正在操作的數組
array.forEach(callback(currentValue, index, array){
//do something
}, this)
var arr= ["a","b","c","d","e","f"];
arr.forEach(function(element) {
console.log(element);
});
arr.forEach( element => console.log(element));
// a
// b
// c
// d
// e
// f
11.map() 方法創建一個新數組，其結果是該數組中的每個元素都調用一個提供的函數後返回的結果
let new_array = arr.map(function callback(currentValue, index, array) { // Return element for new_array }[, thisArg])
- callback：生成新數組元素的函數，使用三個參數：currentValue：
callback 的第一個參數，數組中正在處理的當前元素；index：callback 的第二個參數，數組中正在處理的當前元素的索引；array：callback 的第三個參數，map 方法被調用的數組。 thisArg可選的。執行 callback 函數時 使用的this 值。（一般不使用）
- 例子
var arr= ["a","b","c","d","e","f"];
var result= arr.map( x => x + '1'); //連接符
console.log(arr); //["a","b","c","d","e","f"];
console.log(result);// ["a1", "b1", "c1", "d1", "e1", "f1"]
12.find() 方法返回數組中滿足提供的測試函數的第一個元素的值。否則返回 undefined。
- 語法：arr.find(callback[, thisArg])
- callback：在數組每一項上執行的函數，接收 3 個參數：element：當前遍歷到的元素；index：當前遍歷到的索引；array：數組本身
- 例子
var arr= [
{name: 'a', index: 1},
{name: 'b', index: 2},
{name: 'c', index: 3}
];
function findB(element) {
return element.name === 'b';
}
var result=arr.find(findB)
console.log(result); // { name: 'b', index: 2 }
