JS API summary of Array Operations

One 、 Do not change the method of the original array

1. concat():  Connect Array , Return a new array .
2. slice(): Intercept array , Index based session , Left closed right away .
3. split(): Split a string into strings Array . Such as : ‘a&b&c’.split("&") ==> [a,b,c]
4. join(): Connect the elements in the array with a symbol . Such as ：[a,b,c].join("-") ==> “a-b-c”
5. toString(): Directly convert the array to string format , Comma separated . The effect is the same  arr.join(",")
6. ES6 Deconstruction in : newArr=[…a,…b], Sure Connect Several arrays , The original array does not change .

Two 、 Change the method of the original array

The new result of the original array after these methods , That is, the original array itself .

1. push(): At the end of the array Additional An element , Return array length .
2. pop(): Delete an element at the end of the array , Returns the removed element .
3. length Append at the end : At the end of the array Additional Another way of element , namely arr[arr.length], Return the added element .
4. unshift(): Add an element to the head of the array , Return the added element .
5. shift(): Delete an element in the array header , Returns the deleted element .
6. splice(): Used to add... At the specified location 、 Delete 、 Replacement elements .
   (1)  Delete arr.splice(index,len): From the index index It's about （ Include index, This method includes index In itself , I will not repeat it later ）, The deletion length is len Elements , Returns the composition of deleted elements Array . If I only wrote index, There is no second parameter , From index After the beginning of deletion all Elements .
   (2)  add to arr.splice(index,0,...items)： from index Add several elements at , return [ ] An empty array .（ It can be understood that the replaced element is empty ）arr.splice(arr.length,0,…[1,2,3]):  Connect Array , Append an array at the end [1,2,3] Give the original array .
   (3)  Replace arr.splice(index,len,...items): From the index index Start , Replace  len  Elements , use  items  To replace . if len There are more elements to replace , Then all the remaining ones will be deleted . Returns the composition of the replaced element Array .
7. sort() : Sorting method , In ascending order of strings . In the right order （ Ascending ）: arr.sort((a,b)=>a-b), When a-b When a negative value is returned , The function takes a The order is ratio 100 Smaller values . Such as  10-20= -10
8. reverse(): Inversion array , Reverse the original order , Returns the changed new array .
9. Array.prototype.push.apply(arr1,arr2): On the prototype Connect Array , take arr2 Connected to the arr1 Tail of , The parameter can only be 2 individual , Too many invalid . Return array length ,arr1 Be changed ,arr2 unchanged . arr1.push.apply(arr1,arr2)  The effect is the same .

Continuous document maintenance , If there is something wrong , I hope you can correct or add .