JavaScript Objects Functions and Arrays Explained by Tony de Araujo

Author:Tony de Araujo [de Araujo, Tony]
Language: eng
Format: epub, pdf
Publisher: Tony de Araujo
Published: 2014-05-30T22:00:00+00:00

2.2.8 splice( )

The Array method splice( ) is a very interesting one. Do you still remember push and unshift? they add items to the end or beginning of an array, right? splice() adds items to the middle ( or anywhere in the array).

Let’s see how it works.

Depending on how many arguments you use in the parenthesis, you can the following:

a) Delete items mode:

When you use only two arguments you are giving the index positions of

First argument: where the action is to start (inclusively),

Second argument: How many items will be removed.

Two arguments means deleting because there is nothing to add.

b) Add items mode,

If you insert more than two arguments, the third and consecutive arguments are data to be inserted, and in that case JavaScript assumes you want to insert items into the array.

In juts add mode, the second argument is zero, which means that no items will be deleted in exchange for the items we are adding with the third and consecutive parameters.

c) Replace items mode.

If the second parameter in add mode is anything other than zero, this number will indicate how many items will be deleted in exchange for the items being added.

For example splice(0,3) means to delete 3 items: the first, second and third. Number 3 represents the quantity of items to be removed. The number 3 coincides with the third item on the array but it is not necessarily so. If we had splice(2,3) it would remove the third, fourth and fifth items, which correspond to positions 2,3,4 and counting from zero.

The 3rd and consecutive arguments represent the items to be inserted.

For example, splice(2,0, "yellow") means to insert yellow in position two (third item) and unshift the others because the zero means that no items are to be deleted.

In splice(2,1, "yellow") it means to add yellow to position 2 ( third item) and remove whatever is there (this is a replacement due to the second argument).

The picture below will illustrate the concept:

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