The Array method reverse() in Apps Script

The Array method reverse() reverses the order of elements in an array.

Syntax

array.reverse()

Parameters

The reverse() method does not accept any parameters.

Return value

The reverse() method returns a reference to the array that was reversed.

Examples

Example 1: The reverse() method reverses an array in place

In the code below, the array colors is reversed. Please note that the reverse() method, reverses the array in place - i.e., the colors array is itself reversed.

var colors = ["red", "blue", "green", "black", "orange", "purple"];
colors.reverse();
Logger.log(colors);

Output

[purple, orange, black, green, blue, red]

Example 2: The reverse() method returns a reference to the array that was reversed

The reverse() method does not return a new array. It only returns a reference to the array that was reversed. This is an important concept to understand to ensure your code does not result in unintended consequences.

For example, In the code below, the variable reversedColors contains a reference to the colors array. It is not a new array. So, by adding a new item to the reversedColors array, you're actually adding an item to the colors array. This may not have been your intention and this behavior could lead to unintended consequences or bugs in your program.

var colors = ["red", "blue", "green", "black", "orange", "purple"];
var reversedColors = colors.reverse();
Logger.log(colors);
Logger.log(reversedColors);
Logger.log(colors === reversedColors);

//Add an item to the reversedColors array
reversedColors.push("indigo");
Logger.log(colors);
Logger.log(reversedColors);

Output

[purple, orange, black, green, blue, red]

[purple, orange, black, green, blue, red]

true

[purple, orange, black, green, blue, red, indigo]

[purple, orange, black, green, blue, red, indigo]

Example 3: In the case of two-dimensional arrays, the reverse() method will only apply one level deep. It will not reverse the contents of the inner arrays

The array twoDArray has two inner arrays: [1,2] and [3,4]. The reverse method will not reverse these inner arrays.

var twoDArray = [[1,2],[3,4]];
Logger.log(twoDArray);
Logger.log(twoDArray.reverse());

Output

[[1.0, 2.0], [3.0, 4.0]]

[[3.0, 4.0], [1.0, 2.0]]

Conclusion

In this tutorial, you learned how to use the reverse() method of an array to reverse its contents. Please remember that the reverse() method reverses the array in place. Also, it does not return a new array. Instead, it returns a reference to the array that was reversed.