JavaScript: Reverse Arrays

By  on  

Manipulating data is core to any programming language. JavaScript is no exception, especially as JSON has token over as a prime data delivery format. One such data manipulation is reversing arrays. You may want to reverse an array to show most recent transactions, or simple alphabetic sorting.

Reversing arrays with JavaScript originally was done via reverse but that would mutate the original array:

// First value:
const arr = ['hi', 'low', 'ahhh'];

// Reverse it without reassigning:
arr.reverse();

// Value:
arr (3) ['ahhh', 'low', 'hi']

Modifying the original array is a legacy methodology. To avoid this mutation, we'd copy the array and then reverse it:

const reversed = [...arr].reverse();

These days we can use toReversed to avoid mutating the original array:

const arr = ['hi', 'low', 'ahhh'];
const reversed = arr.toReversed(); // (3) ['ahhh', 'low', 'hi'];
arr; // ['hi', 'low', 'ahhh']

Avoiding mutation of data objects is incredibly important in a programming language like JavaScript where object references are meaningful.

Recent Features

  • By
    9 Mind-Blowing Canvas Demos

    The <canvas> element has been a revelation for the visual experts among our ranks.  Canvas provides the means for incredible and efficient animations with the added bonus of no Flash; these developers can flash their awesome JavaScript skills instead.  Here are nine unbelievable canvas demos that...

  • By
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

Incredible Demos

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!