Library for manipulating text ranges and selections, and assorted other programs that use that

View the Project on GitHub dwachss/bililiteRange

bililiteRange data

Often, we want to keep data that is specific to a given element, and shared by all ranges on that element. Simply setting = bar works, but in the olden days (Internet Explorer 6) that caused memory leaks. That is no longer a problem, but putting so many new fields on the element lacks a certain elegance. So we create a single field, element.bililiteRangeData, and store all our fields in that, with = bar.

To avoid any possibility of a name conflict, we use a private variable const dataKey = Symbol() and actually do element[dataKey].foo. To expose that (since dataKey is not exposed) we define for each range = range.element[dataKey].

So, for example,

let range = bililiteRange( document.querySelector('div.editor') ); = 'Prism';

// elsewhere in the code
let range2 = bililiteRange( document.querySelector('div.editor') );
console.log(; // 'Prism'


That works well, but I created bililiteRange in part to implement the ex line editor, and I want some data to have default values that can be changed for each element. So data is actually an object with a prototype. bililiteRange.createOption(prop, descriptor) does Object.defineProperty(data.prototype, prop, descriptor). Now every range has a property prop with an object descriptor.

So to set autoindent, do bililiteRange.createOption('autoindent', {value: false}).

The difference with Object.defineProperty is that the defaults are { enumerable: true, writable: true, configurable: true } rather than false.

Monitored options

There is one more option that can be added to the property descriptor: monitored. bililiteRange.createOption(prop, {monitored: true}) adds a set handler for prop that, whenever prop is set (as in[prop] = newValue), that change is signaled in two ways:

  1. range.dispatch(CustomEvent(`data-${prop}`, {detail: newValue})) for use with EventListeners.

  2. range.element.setAttribute(`data-${prop}`, newValue) for use with MutationObservers. Note that attributes have very limited legal characters, so this will silently fail if data-${prop} is not a legal attribute name.


The function will trigger the CustomEvent and setAttribute for all monitored options. This is useful for initializing things after defining the data, without setting options to differ from their defaults. Call this after all your bililiteRange.createOptions (the program can’t call this automatically since there’s no way to know when the user is done).


bililiteRange.prototype.ex uses JSON.stringify to display options. The data object, therefore has a toJSON method that only returns data fields that were defined with bililiteRange.createOption and are defined on this particular element.


bililiteRange.createOption('foo', {value: 1}); // data created for all bililiteRange's
bililiteRange.createOption('bar', {value: 2});

const range = bililiteRange(element); = 3; // data created for this bililiteRange's element only = 7; // modify an option created above.

console.log( JSON.stringify( ); // {"foo":7}
console.log( JSON.stringify( ); // {"foo":7,"bar":2}

If you really want to stringify all of, use JSON.stringify( Object.assign({}, to copy it.

“Reserved” fields

The following are data fields used by this package:

bililiteRange.js: mousetime, liveRanges, oldText, selection, sendkeysBounds, sendkeysOriginalText

bililiteRange.undo.js: undos

bililiteRange.lines.js: autoindent, tabsize

bililiteRange.find.js: bigwords, dotall, global, ignorecase, magic, multiline, sections, sentences, unicode, words, wrapscan

bililiteRange.ex.js: directory, file, reader, stderr, stderr, savestatus, writer