bindcache

BindCache

It caches/memoizes result of binding function with its context and args. For the same set it returns identical result every time.

This version uses es6-map and es6-weak-map shims from your peerDependencies. If you don't need them or you use other shims for Map and WeakMap you should use cachebind instead of this.

Motivation

It solves the problem of unnecessary renders cased by use of Function.prototype.bind function in render method. It also keep up with jsx-no-bind rule which is used to detect such issues.

class MyComponent extends Component {
    onChange() {
        // ...    
    }

    render () {
        const { param } = this.props
        return (
            <div>
                <SomeComponent someParam={"value"}>
                <OtherComponent callback={this.onChange.bind(this, param, "MyComponent")}/>
            </div>    
        )
    }
}

This code will make OtherComponent to render every time this render function will be fired.

Api

If you need to bind context:

bind(context: any, fn: () => void, args?: any | Array<any>)

If you don't need context:

bindArgs(fn: () => void, args?: any | Array<any>)

• context — context,
• fn — function to bind,
• args — any number of arguments of any type devided by commas.

Usage

npm install bindcache

import { bind } from "bindcache"

class MyComponent extends Component {
    onChange(param, component) {
        // ...
    }

    render () {
        const { param } = this.props
        return (
            <div>
                <SomeComponent someParam={"value"}>
                <OtherComponent callback={bind(this, this.onChange, param, "MyComponent")}/>
            </div>    
        )
    }
}

If you don't need the context of the function or it is already present/binded you can use bindArgs util instead. The previous code can be written like this.

import { bindArgs } from "bindcache"

class MyComponent extends Component {
    onChange = (param, component) => { /* ... */ }

    render () {
        const { param } = this.props
        return (
            <div>
                <SomeComponent someParam={"value"}>
                <OtherComponent callback={bindArgs(this.onChange, param, "MyComponent")}/>
            </div>
        )
    }
}

bindArgs(fn, ...args) is equal to bind(undefined, fn, ...args)

How it works

The util caches results of binding in native WeakMap so the items with no references can be garbage collected.

Tips

bind util lets you feed it with context for the function. You can use arrow function (as it was shown above), or bind context once with decorator:

class MyComponent extends Component {
    @autoBind
    onChange(param, component) {
        // ...
    }
    // ...
}

or cache the result of binding in constructor:

class MyComponent extends Component {
   constructor(props) {
       super(props)
       this.onChange = this.onChange.bind(this)
   }

   onChange(param, component) {
       // ...
   }
   // ...
}

It is not suggested to use this utils instead of Function.prototype.bind in every case. The original bind function is still faster. For example if you need to bind context with no args or your params are static for the component you can bind it one time in constructor function. But it will help you great deal in case of unnecessary renders of react components.