jQuery plugin for highlighting bits of text within a textarea.
JavaScript HTML CSS

README.md

highlight-within-textarea

jQuery plugin for highlighting bits of text within a textarea.

Introduction

It's not actually possible to style text in a textarea, because any markup within a textarea is treated as plain text. This plugin aims to fake it, allowing you to highlight pieces of text inside a textarea.

A native textarea element is used and familiar properties (auto-correct, scrolling, resizing, etc.) work as expected.

Usage

To see examples in action, check out the demo page.

Make sure you reference both the CSS and the JS files on your page. Then you can use the plugin like this:

function onInput(input) {
    // do stuff, return something
}

$('.my-textarea').highlightWithinTextarea(onInput);

The plugin takes a callback function that is called every time the textarea's input changes. Its job is to indicate which bits of text should be highlighted. There are a couple ways to do this, depending on the type of what is returned, as outlined below.

Regex

If a RegExp object is returned, then any text matching the pattern will be highlighted.

Example:

function onInput(input) {
    return /\w+/g;
}
Array

The function may also return an array of arrays. Each inner array specifies a span of highlighting and should have exactly 2 values: the starting character index (inclusive) and the ending character index (exclusive).

Example:

function onInput(input) {
    return [[0, 5], [10, 15]];
}
Something Falsey

Returning any falsey value (false, undefined, null, 0, '', or NaN) will highlight nothing.

Example:

function onInput(input) {
    return false;
}

Styling

For reference, the demo page has some sample styling.

There are a few guidelines for getting your styles in the right places. Here are the classes you'll want to use.

.hwt-container

Use for background, positioning, and visibility (display, margin, position, top, left, background, etc.).

.hwt-content

Use for sizing and text formatting (width, height, padding, border, color, font, etc.).

.hwt-content mark

Use for highlighted text. Generally, stuff that doesn't change size is fine (background-color, border-radius, box-shadow, etc.). Changes to color won't be visible, since text in the textarea covers colored text in the highlights.

Destroying

You can remove the plugin from a textarea with this:

$('.my-textarea').data('hwt').destroy();