5.4.3 • Public • Published

nanomorph stability

npm version build status downloads js-standard-style

Hyper fast diffing algorithm for real DOM nodes


var morph = require('nanomorph')
var html = require('nanohtml')

var tree = html`<div>hello people</div>`
// document.body === <body><div>hello people</div></body>

morph(tree, html`<div>nanananana-na-no</div>`)
// document.body === <body><div>nanananana-na-no</div></body>

morph(tree, html`<div>teeny, tiny, tin bottle</div>`)
// document.body === <body><div>teeny, tiny, tin bottle</div></body>

Clearing Input Values

To remove values from inputs, there's a few options:

html`<input class="beep" value=${null}>` // set the value to null
html`<input class="beep">`               // omit property all together

Reordering Lists

It's common to work with lists of elements on the DOM. Adding, removing or reordering elements in a list can be rather expensive. To optimize this you can add an id attribute to a DOM node. When reordering nodes it will compare nodes with the same ID against each other, resulting in far fewer re-renders. This is especially potent when coupled with DOM node caching.

var el = html`
    <div id="first">hello</div>
    <div id="second">world</div>

Caching DOM elements

Sometimes we want to tell the algorithm to not evaluate certain nodes (and its children). This can be because we're sure they haven't changed, or perhaps because another piece of code is managing that part of the DOM tree. To achieve this nanomorph evaluates the .isSameNode() method on nodes to determine if they should be updated or not.

var el = html`<div>node</div>`

// tell nanomorph to not compare the DOM tree if they're both divs
el.isSameNode = function (target) {
  return (target && target.nodeName && target.nodeName === 'DIV')

Prevent Morphing Particular Elements

There are situations where two elements should never be morphed, but replaced. nanomorph automatically does this for elements with different tag names. But if we're implementing a custom component system, for example, components of different types should probably be treated as if they had different tags—even if they both render a <div> at their top level.

Nodes can have an optional data-nanomorph-component-id attribute. nanomorph will only ever morph nodes if they both have the same value in this attribute. If the values differ, the old node is replaced with the new one.

var el = html`<div data-nanomorph-component-id="a">hello</div>`
var el2 = html`<div data-nanomorph-component-id="b">goodbye</div>`

assert.equal(nanomorph(el, el2), el2)

nanomorph doesn't have an opinion on the values of the data-nanomorph-component-id attribute, so we can decide the meaning we give it on a case by case basis. There could be a unique ID for every type of component, or a unique ID for every instance of a component, or any other meaning.


How is this different from morphdom?

It's quite similar actually; the API of this library is completely compatible with morphdom and we've borrowed a fair few bits. The main difference is that we copy event handlers like onclick, don't support browsers that are over a decade old, and don't provide custom behavior by removing all hooks. This way we can guarantee a consistent, out-of-the box experience for all your diffing needs.

Why doesn't this work in Node?

Node has no concept of a DOM - server side rendering is basically fancy string concatenation. If you want to combine HTML strings in Node, check out hyperstream.

This library seems cool, I'd like to build my own!

Nanomorph was optimized for simplicity, but different situations might require different tradeoffs. So in order to allow folks to build their own implementation we expose our test suite as a function you can call. So regardless if you're doing it to solve a problem, or just for fun: you can use the same tests we use for your own implementation. Yay!


tree = nanomorph(oldTree, newTree)

Diff a tree of HTML elements against another tree of HTML elements and create a patched result that can be applied on the DOM.

⚠️ nanomorph will modify the newTree and it should be discarded after use


$ npm install nanomorph

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