Click the button to add elements to the array.
Note: The unshift() method does not work properly in Internet Explorer 8 and earlier, the values will be inserted, but the return value will be undefined.
Definition and Usage The unshift() method adds new items to the beginning of an array, and returns the new length. Note: This method changes the length of an array. Tip: To add new items at the end of an array, use the push() method.