1: splice method in js
splice(index,len,[item]) Note: This method changes the original array.
splice has 3 parameters, it can also be used to replace/delete/add one or several values in the array
index: the starting subscript of the array len: the length of the replacement/deletion item: the value of the replacement, the item is empty for the deletion operation
Such as: arr = ['a','b','c','d']
Delete---- item is not set
arr.splice(1,1) //['a','c','d'] delete a value with a starting subscript of 1 and a length of 1, len is set to 1, if it is 0, the array is not Change
arr.splice(1,2) //['a','d'] delete a value whose starting subscript is 1 and length is 2, and len is set to 2
Replace ---- item is the replaced value
arr.splice(1,1,'ttt') //['a','ttt','c','d'] Replace the starting subscript with 1 and a value with length 1 of 'ttt', len set to 1
arr.splice(1,2,'ttt') //['a','ttt','d'] Replace the starting subscript with 1 and the two values with length 2 as 'ttt', set by len 1
Add ---- len is set to 0, item is the added value
arr.splice(1,0,'ttt') //['a','ttt','b','c','d'] means adding an item 'ttt' at subscript 1
It seems that splice is the most convenient.
2: After delete delete deletes the elements in the array, it will set the value of the subscript to undefined, and the length of the array will not change
For example: delete arr[1] //['a', ,'c','d'] There are two commas in the middle, the length of the array is unchanged, and one item is undefined
There are several other custom methods, refer to here