What are the methods of adding elements to arrays in JS

js How to add elements to an array in
unshift： Add parameters to the beginning of the original array , And returns the length of the array
pop： Delete the last item of the original array , And returns the value of the deleted element ; Returns if the array is empty undefined
push： Add the parameter to the end of the original array , And returns the length of the array
concat： Returns a new array , It is composed of adding parameters to the original array
splice(start,deleteCount,val1,val2,…)： from start Location start delete deleteCount term , And insert... From this position val1,val2,…
reverse： Reverse the array
sort(orderfunction)： Sort the array by the specified parameters
slice(start,end)： Returns a new array of items from the specified start subscript to the end subscript in the original array

detailed ：
1、 Array creation
var arrayObj = new Array();　// Create an array
var arrayObj = new Array([size]);　// Create an array and specify the length , Note that it's not the upper limit , It's length.
var arrayObj = new Array([element0[, element1[, …[, elementN]]]]);　 Create an array and assign
It should be noted that , Although the second way to create an array specifies the length , But in fact, in all cases, arrays are longer , That is to say, even if the specified length is 5, You can still store elements outside the specified length , Be careful ： Then the length will change .

2、 Access to elements of an array
var testGetArrValue=arrayObj[1]; // Get element value of array
arrayObj[1]= “ This is the new value. ”; // Assign new values to array elements

3、 Adding array elements
arrayObj. push([item1 [item2 [… [itemN ]]]]);// Add one or more new elements to the end of the array , And returns the new length of the array
arrayObj.unshift([item1 [item2 [… [itemN ]]]]);// Add one or more new elements to the beginning of the array , Elements in an array are automatically moved back , Returns the new length of the array
arrayObj.splice(insertPos,0,[item1[, item2[, … [,itemN]]]]);// Inserts one or more new elements into the array at the specified location , Automatic backward movement of elements in insertion position , return ”“.

4、 Deletion of array elements
arrayObj.pop(); // Remove the last element and return the element value
arrayObj.shift(); // Remove the previous element and return the element value , Elements in array move forward automatically
arrayObj.splice(deletePos,deleteCount); // Delete from specified location deletePos Specified number of starts deleteCount The elements of , Array returns the removed element

5、 Array truncation and merging
arrayObj.slice(start, [end]); // Returns a part of an array as an array , Note not included end Corresponding elements , If omitted end Will be copied start All elements after
arrayObj.concat([item1[, item2[, … [,itemN]]]]); // Multiple arrays （ It could be a string , Or a mix of arrays and strings ） Join as an array , Return the new array connected
Arrangement ：www.mls169.com

6、 Copy of array
arrayObj.slice(0); // Returns the copy array of the array , Notice it's a new array , Not pointing
arrayObj.concat(); // Returns the copy array of the array , Notice it's a new array , Not pointing

7、 Sorting of array elements
arrayObj.reverse(); // Reversal element （ Top to bottom 、 The last to the top ）, Return array address
arrayObj.sort(); // Sort array elements , Return array address

8、 String of array elements
arrayObj.join(separator); // Return string , This string joins the values of each element of the array together , Intermediate use separator separate .
toLocaleString 、toString 、valueOf： It can be seen as join Special use of , Not commonly used