Géry Debongnie
7.0 KiB
Comparison with Vue/React
OWL, React and Vue have the same main feature: they allow developers to build declarative user interfaces. To do that, all these frameworks uses a virtual dom. However, there are still obviously many differences.
In this page, we try to highlight some of these differences. Obviously, some effort was done to be fair. However, if you disagree with some of the points discussed, feel free to open an issue/submit a PR to correct this text.
Size
OWL is intended to be small and to work at a slightly lower level of abstraction than React and Vue. Also, jQuery is not the same kind of framework, but it is interesting to compare.
| Framework | Size (minified) | Size (minified, gzipped) |
|---|---|---|
| OWL | 32kb | 11kb |
| Vue + VueX | 30kb | |
| React + ReactDOM + Redux | 40kb | |
| jQuery | 86kb | 30kb |
Tooling/Build step
OWL is designed to be easy to use in a standalone way. For various reasons, Odoo does not want to rely on standard web tools (such as webpack), and OWL can be used by simply adding a script tag to a page.
<script src="owl.min.js" />
In comparison, React encourages using JSX, which necessitate a build step, and most Vue applications uses single file components, which also necessitate a build step.
On the flipside, external tooling may make it harder to use in some case, but it also brings a lot of benefits. And React/Vue have both a large ecosystem.
Templating
OWL uses its own QWeb engine, which compiles templates on the frontend, as they are needed. This is extremely convenient for our use case, in particular because templates are described in XML files, and can be modified by XPaths. Since Odoo is at its heart a modular application, this is an important feature for us.
<div>
<button t-on-click="increment">Click Me! [<t t-esc="state.value"/>]</button>
</div>
Vue is actually kind of similar. Its template language is kind of close to QWeb,
with the v replaced by the t. However, it is also more fully featured. For
example, Vue templates have slots, or event modifiers. A large difference is that
most Vue applications will need to be built ahead of time, to compile the templates
into javascript functions. Note that Vue has a separate build which includes the
template compiler.
In contrast, most React applications do not use a templating language, but write some JSX code, which is precompiled into plain JavaScript by a build step.
class Clock extends React.Component {
render() {
return (
<div>
<h1>Hello, world!</h1>
<h2>It is {this.props.date.toLocaleTimeString()}.</h2>
</div>
);
}
}
This has the advantage of having the full power of Javascript, but is less structured than a template language. Note that the tooling is quite impressive: there is a syntax highlighter for jsx here on github!
Asynchronous rendering
This is actually a big difference between OWL and React/Vue: components in OWL are totally asynchronous. They have two asynchronous hooks in their lifecycle:
willStart(before the widget starts rendering)willUpdateProps(before new props are set)
Both these methods can be implemented and return a promise. The rendering will then wait for these promises to be completed before patching the DOM. This is useful for some use cases: for example, a widget may want to fetch an external library (a calendar widget may need a specialized calendar rendering library), in its willStart hook.
class MyCalendarWidget extends owl.Component {
...
willStart() {
return utils.lazyLoad('static/libs/fullcalendar/fullcalendar.js');
}
...
}
This may be dangerous (to stop the rendering waiting for the network), but it is extremely powerful as well, as demonstrated by the Odoo Web Client.
Lazy loading static libraries can obviously be done with React/Vue, but it is more convoluted.
Reactiveness
React has a simple model: whenever the state changes, it is replaced with a new state (via the setState method). Then, the DOM is patched. This is simple, efficient, and a little bit awkward to write.
Vue is a little bit different: it replace magically the properties in the state by getters/setters. With that, it can notify components whenever the state that they read was changed.
Owl is closer to vue: it also tracks magically the state properties, but it does only increment a counter whenever it changes (and a deep counter for each of its parents). This assumes that the state is actually a tree.
State Management
Managing the state of an application is a tricky issue. Many solutions have been proposed these last few years. It also depends on the kind of application we are talking about. A small application may not need much more than a simple object to contain its state.
However, there are some common solutions for React and Vue: redux and vuex. Both of them are a centralized store that own the state, and they dictate how the state can be mutated.
Redux
In Redux, the state is mutated by reducers. Reducers are functions that modify the state by returning a different object:
...
switch (action.type) {
case ADD_TODO: {
const { id, content } = action.payload;
return {
...state,
allIds: [...state.allIds, id],
byIds: {
...state.byIds,
[id]: {
content,
completed: false
}
}
};
}
This is a little bit awkward to write, but this allows the component system to
check if a part of the state was changed. This is exactly what is done by the
connect function: it create a connected component, which is subscribed to
the state and triggers a rerender if some part of the state was modified.
VueX
VueX is based on a different principle: the state is mutated through some special functions (the mutations), which modify the state in place:
function ({state}, payload) {
const { id, content } = payload;
const message = {id, content, completed: false};
state.messages.push(message)
}
This is simpler, but there is a little bit more happening behind the scene: each key from the state is silently replaced by getters and setters, and VueX keeps track of who get data, and retrigger a render when it was changed.
Owl
Owl store is a little bit like a mix of redux and vuex: it has mutations and actions, like VueX, it keeps track of the state changes, but it does not notify a component when the state changes. Instead, components need to connect to the store like in redux, with a function that will listen to the relevant state.