#react-lazy-cache
[](https://www.npmjs .com/package/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.
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 (<div>
<div>Sum: {sum}</div>
<div>Difference: {difference}</div>
<div>Product: {product}</div>
<div>Quotient: {quotient}</div>
<div>Sum Squared: {sumSquared}</div>
</div>);
}
}
Two things to notice about the above example:
The values do not get calculated until the properties on the cache
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.
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!
That's all you need to know! Go forth and intelligently cache your calculated values!
Feedback welcome.