Common methods of JS array

reverse Flip
sort Sort
push Add... From the back
unshift Add... From the front
pop Delete... From the back
shift Remove... From the front
indexOf From front to back string index
lastIndexOf String index from back to front
join,toString Convert to string type , It is recommended to use join
concat Become
slice Intercept （ A large array is only a part of a fragment ）
splice Delete

How arrays are created （ Get to know ）
I can only write it literally

Type of data
Simple data type ：number,string,boolean,null,undefined （null It's printed out object)
Composite data type , Complex data type ：array,object ( Array is also a special kind of object ）

We can't get through typeof To detect whether a data is an array , Use other ways to detect ：
1. data instanceof Array true The description is an array
2. Array.isArray( data ）true The description is an array
 

Array add elements
1. push PUSH Add at the back （ The most used ）
2. unshift Add... To the front
3. pop Remove the last one
4. shift Remove the first one

sort Method in use , The default is to convert all data into strings , Then press ascii Compare in order
Primacy and primacy comparison

reverse() Flip array
sort(function(a,b){return a - b;})

If you ask bubble sort , --> double for Cyclic writing

Find whether the element is in the array , Position in array （ The first index value ）, If not, the return value is -1
indexOf Look back before （ Commonly used ）
lastIndexOf Look backwards

indexOf Has two functions
1. You can detect the position of elements in the array
2. You can detect whether there is this element in the array （ duplicate removal ）