A utility to lazily calculate and cache values in a react component based on props
npm install react-lazy-cache#react-lazy-cache
react-lazy-cache is a utility to lazily calculate and cache values in a React component based on props.
``
npm install --save react-lazy-cache
Ideally, in a React component, you would calculate values that depend on your props inputs every time the component
is rendered. However, in practice, sometimes these values, either for computational or memory reasons, are better off
cached. When you cache them, however, you need to be constantly watching your props to know if you need to
invalidate your cache and recalculate those values. _That_ is what react-lazy-cache does for you.
react-lazy-cache could not be simpler to use. You simply need to give it a map of calculations, and let it know
when your component will receive new props.
`javascript
import React, {Component, PropTypes} from 'react';
import lazyCache from 'react-lazy-cache';
export default class Arithmetic extends Component {
static propTypes = {
a: PropTypes.number.isRequired,
b: PropTypes.number.isRequired
}
componentWillMount() {
// create cache
this.cache = lazyCache(this, {
sum: {
params: ['a', 'b'],
fn: (a, b) => a + b
},
difference: {
params: ['a', 'b'],
fn: (a, b) => a - b
},
product: {
params: ['a', 'b'],
fn: (a, b) => a * b
},
quotient: {
params: ['a', 'b'],
fn: (a, b) => a / b
},
sumSquared: {
params: ['sum'],
fn: (sum) => sum * sum
}
});
}
componentWillReceiveProps(nextProps) {
this.cache.componentWillReceiveProps(nextProps);
}
render() {
const {sum, difference, product, quotient, sumSquared} = this.cache;
return (
Two things to notice about the above example:
$3
The values do not get calculated until the properties on the
object get referenced in render().
That's why it's "lazy". They will not be calculated again unless one of the props that the calculation depends on
changes.$3
When you specify your functions to calculate each value, you must specify the params, which refer either to props
given to your React component, _or_ to other calculated values (see: sumSquared).Be careful to not cause an infinite dependency loop!
$3
As this library utilizes Getters, which are not shimmable in IE8 and older, an alternate
noGetters module is exposed.
This version allows you to cache values, but are not able to inject other values such as sumSquared. Usage:`javascript
import LazyCache from 'react-lazy-cache/noGetters';const cache = new LazyCache(...) // same signature as normal version
const sum = cache.get('sum');
`The difference is that it's a class and not a plain function (so you have to
it), and properties are accessed
through the get`-function, instead of as a property.That's all you need to know! Go forth and intelligently cache your calculated values!
Feedback welcome.