babel-plugin-promote-class-properties
v0.0.1
Published
Babel plugin to replace old code using ClassProperties feature
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babel-plugin-promote-class-properties
Babel plugin to replace old code taking advantage of ClassProperties feature
Before
class Foo {
constructor() {
this.foo = this.foo.bind(this);
this.bar = this.bar.bind(this);
}
foo(arg1, arg2) {
console.log(arg1, arg2)
}
bar(lol) {
return lol;
}
}
After
class Foo {
foo = (arg1, arg2) => {
console.log(arg1, arg2)
}
bar = (lol) => {
return lol;
}
}
Installation
Motivation
Declaring event listeners is a common thing to do on the daily bases of every JS developer. In real life applications we see a lot of this:
class App extends React.Component {
constructor() {
this.onLoad = this.onLoad.bind(this);
this.state = {width: 0, height: 0};
}
onLoad({target: {height, width}}) {
this.setState({width, height});
}
render() {
const {width, height} = this.state;
return (
<div>
<div>{width}x{height}</div>
<img onLoad={this.onLoad} />
</div>
);
}
}
We need to do
this.onLoad = this.onLoad.bind(this);
Because of the way of this context is handled on addEventListener
, see The_value_of_this_within_the_handler, from MDN:
If attaching a handler function to an element using addEventListener(), the value of this inside the handler is a reference to the element. It is the same as the value of the currentTarget property of the event argument that is passed to the handler.
Doing that reassignment, we keep the react component instance as this value and we can do operations like setState
while still having access to the DOM element.
TODO
- Remove empty constructor
- Handle inline cases =>
<img onError={this.onImgError.bind(this) />
- Handle =>
document.body.addEventListener('scroll', this.onScroll.bind(this));