Mutate

Mutate is a library of helpers to maintain persistent modifications to the rendered DOM of a web page for implementation of temporary, experimental changes and features for rapid experimentation.

It is intended to be framework independent and equally effective for SPAs and traditionally rendered webpages.

Getting Set Up

Installation

$ npm install @evolv/mutate

Building From Source

Clone the repository and run the following commands.

$ npm install
$ npm run build

Run Demo Website

There is a demo site included.

Content warning: flashing lights

$ npm run demo

Getting Started

The API for Mutate is similar in a lot of ways to the API of jQuery with a significant difference, that is selectors (Collectors) refer to all current and future matching Elements, and the functions to modify the DOM (Mutations) are persistent.

This means that you don't need to worry about timing, or dynamic areas of the rendered page.

Mutate also provides the ability to "project" Elements of the DOM into other Elements of the DOM, binding all interactions with the "projection" back to the original Elements.

As everyone building variants have learned the hard way, most Elements are dependent on their location in the DOM for both style and functionality. Projection allows the implementer to "move" and restyle Elements without losing the position dependent functionality of the original Elements.

Importing

import {collect, mutate} from '@evolv/mutate';

Basic Usage

The basic flow when using Mutate is to first define a Collector.

collect('<selector>', '<collector name>');

Then to define a Mutator for the Collector.

mutate('<collector name>').hide();

Mutators allow for Mutations to be chained together, similar to jQuery which will be evaluated in order of invocation.

mutate('<collector name>').text('<new text value>').classes({'<new class>': true});

Loop Guard (Infinite Loop Protection)

Mutate can detect runaway collectors (e.g. when a mutation keeps creating elements that re-trigger its own collector) and automatically pause the affected mutators.

Enable and configure the loop guard at bootstrap time:

import { bootstrap } from '@evolv/mutate';

bootstrap({
  loopGuard: {
    enabled: true,
    windowMs: 1000,   // size of the observation window
    threshold: 10,    // max collector events allowed within the window
    cooldownMs: 5000, // time to wait before the same collector can trigger again
    onDetect: (event) => {
      console.warn('Loop detected', event);
    },
  },
});

You can also toggle or reconfigure it at runtime through collect.loopGuard, either via the module export or the global evolv.collect.loopGuard once bootstrapped:

import { collect } from '@evolv/mutate';

collect.loopGuard.enable({ threshold: 3, windowMs: 500 });
// To disable again:
evolv.collect.loopGuard.disable();

Every detection dispatches a evolv:mutate-loop-detected CustomEvent so host applications can listen globally:

document.addEventListener('evolv:mutate-loop-detected', (event) => {
  console.log('Loop guard tripped', event.detail);
});

When the guard trips, the relevant collector is paused, and the active mutators are paused & reverted so the page remains responsive.

Notes

• The guard is disabled by default; enable it explicitly and tune threshold, windowMs, and cooldownMs (default 5000ms) for your scenario. Starting with a higher threshold (default 10 events within 1000ms) avoids flagging legitimate quick mutations such as text() + styles().
• Built-in effects automatically revert, but custom mutations must provide a revert handler if you expect the guard to undo their DOM changes.

How to test your changes

1. Run npm start
2. Create a simple website or use codesandbox
3. Add a snippet to head <script src="http://localhost:8080/index.js"></script> (make sure that your local is running on 8080, otherwise update src)
4. Apply changes to the website in the console

evolv.collect('h1', 'heading')
evolv.mutate('heading').html('Test');

Documentation

Mutate Documentation