javascript spliceJavaScript’s Array.prototype.splice() method removes one or more elements from any position in the array and returns the removed elements in a new array. It also allows you to add one or more elements to the middle of an array.

JavaScript’s Array.prototype.shift() and Array.prototype.pop() methods allow you to remove elements from the beginning and end of a JavaScript array. These methods are simple to use and require no arguments because there is no potential for ambiguity: the concepts “first element” and “last element” require no further explanation. But when you want to remove one or more elements from the middle of a JavaScript array, there are details required. For example: where in the array do we want to start removing elements? Also, how many elements do we want to remove?

The Array.prototype.splice() method answers that question by removing one or more elements from any position in the array and returning the removed elements in a new array. Initially, this can throw you off because if you want to remove only one element, you would expect just that one element to be returned. But the Array.prototype.splice() method always returns an array. So, just keep in mind that if you plan to remove one element, you’ll need to access the first element in the array that is returned.

The syntax for this is simple: you just pass a minimum of two numbers to the splice() method: the position in the array at which you want to start removing elements, and the number of elements to remove. In this case, you are only removing elements from the array. But you do have the option of adding as many additional parameters as you like. So, beginning with the 3rd parameter, you specify one or more elements to ADD to the array, starting at the position specified with the first parameter. For example: myArray.splice(2, 3) would remove three elements from myArray, starting at index # 2. But, myArray.splice(2, 3, ‘a’, ‘b’, ‘c’) would also add the strings ‘a’, ‘b’, ‘c’ to the array starting at index # 2.

JavaScript’s Array.prototype.unshift() and Array.prototype.push() methods allow you to remove elements from the beginning and end of a JavaScript array. But if you want to remove elements from the middle of an array, the Array.prototype.splice() method is the correct tool. In this case, you provide a zero as the 2nd argument, which means that you are saying: “I do not want to remove any elements from the array”. If you provide any arguments after the 2nd argument, however, then those will be added to the array starting at the position specified in the 1st argument. For example: myArray.splice(2, 0, ‘HELLO’, ‘GOODBYE’). Here, you’d be adding the strings ‘HELLO‘, ‘GOODBYE‘ to the array starting at position # 2. But keep in mind that in this case, the Array.prototype.splice() method will return an empty array, because that method always returns an array. But if you do not remove any elements from the original array, then an empty array is returned.

Try it yourself !

In the above example, click the JavaScript tab. There we call the splice method on an array. In the first case, we take a very simple approach; the first argument is 0 and the second argument is 1: foo.splice(0, 1). This is similar to using the JavaScript shift() method, except that shift() returns the removed element, whereas the splice() method returns the removed element in an array.  This is a very simple example, but the main takeaway is: the first argument is the position to start at, and the second argument is the number of elements to remove.

Later in the examples, we pass no arguments to the splice method. In this case, no elements are removed from the original array and an empty array is removed.

Click the Result tab to see the output for all of the splice method examples.

Starting from the end of the array

In the last example, we provide a negative number for the first argument. A negative number tells the splice method that we want to “start at the end”.  For example:   foo.splice(-4, 3)  tells that splice method that we want to start at the fourth-to-last element in the array, and remove three elements.

Summary

Working with the beginning or the end of a JavaScript array is fairly straightforward, and to make matters even better, the Array.prototype’s push(), pop(), shift() and unshift() methods simplify the process. It’s when you want to remove or add elements to the middle of an array that things can get a bit more complex. Fortunately, though, the Array.prototype.splice() method provides a way to remove one or more elements from or add elements to the middle of a JavaScript array. But the key thing to remember is: this method always returns an array. So, if you are removing elements and you want to access any of the removed elements, you’ll need to iterate the returned array. But if you are adding elements only, then an empty array will be returned.

Leave a Reply

Your email address will not be published. Required fields are marked *