typescript-memoize
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    1.0.1 • Public • Published

    typescript-memoize

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    A memoize decorator for Typescript.

    Installation

    npm install --save typescript-memoize
    

    Usage:

    @Memoize(hashFunction?: (...args: any[]) => any)

    You can use it in four ways:

    • Memoize a get accessor,
    • Memoize a method which takes no parameters,
    • Memoize a method which varies based on its first parameter only,
    • Memoize a method which varies based on some combination of parameters

    You can call memoized methods within the same class, too. This could be useful if you want to memoize the return value for an entire data set, and also a filtered or mapped version of that same set.

    Memoize a get accessor, or a method which takes no parameters

    These both work the same way. Subsequent calls to a memoized method without parameters, or to a get accessor, always return the same value.

    I generally consider it an anti-pattern for a call to a get accessor to trigger an expensive operation. Simply adding Memoize() to a get allows for seamless lazy-loading.

    import {Memoize,MemoizeExpiring} from 'typescript-memoize';
    
    class SimpleFoo {
    
        // Memoize a method without parameters
        @Memoize()
        public getAllTheData() {
           // do some expensive operation to get data
           return data;
        }
    
        // Memoize a method and expire the value after some time
        @MemoizeExpiring(5000)
        public getDataForSomeTime() {
            // do some expensive operation to get data
            return data;
        }
    
        // Memoize a getter
        @Memoize()
        public get someValue() {
            // do some expensive operation to calculate value
            return value;
        }
    
    }

    And then we call them from somewhere else in our code:

    let simpleFoo = new SimpleFoo();
    
    // Memoizes a calculated value and returns it:
    let methodVal1 = simpleFoo.getAllTheData();
    
    // Returns memoized value
    let methodVal2 = simpleFoo.getAllTheData();
    
    // Memoizes (lazy-loads) a calculated value and returns it:
    let getterVal1 = simpleFoo.someValue;
    
    // Returns memoized value
    let getterVal2 = simpleFoo.someValue;

    Memoize a method which varies based on its first parameter only

    Subsequent calls to this style of memoized method will always return the same value.

    I'm not really sure why anyone would use this approach to memoize a method with more than one parameter, but it's possible.

    import {Memoize} from 'typescript-memoize';
    
    class ComplicatedFoo {
    
    	// Memoize a method without parameters (just like the first example)
    	@Memoize()
    	public getAllTheData() {
    		// do some expensive operation to get data
    		return data;
    	}
    
    	// Memoize a method with one parameter
    	@Memoize()
    	public getSomeOfTheData(id: number) {
    		let allTheData = this.getAllTheData(); // if you want to!
    		// do some expensive operation to get data
    		return data;
    	}
    
    	// Memoize a method with multiple parameters
    	// Only the first parameter will be used for memoization
    	@Memoize()
    	public getGreeting(name: string, planet: string) {
    		return 'Hello, ' + name + '! Welcome to ' + planet;
    	}
    
    }

    We call these methods from somewhere else in our code:

    let complicatedFoo = new ComplicatedFoo();
    
    // Returns calculated value and memoizes it:
    let oneParam1 = complicatedFoo.getSomeOfTheData();
    
    // Returns memoized value
    let oneParam2 = complicatedFoo.getSomeOfTheData();
    
    // Memoizes a calculated value and returns it:
    // 'Hello, Darryl! Welcome to Earth'
    let greeterVal1 = complicatedFoo.getGreeting('Darryl', 'Earth');
    
    // Ignores the second parameter, and returns memoized value
    // 'Hello, Darryl! Welcome to Earth'
    let greeterVal2 = complicatedFoo.getGreeting('Darryl', 'Mars');

    Memoize a method which varies based on some combination of parameters

    Pass in a hashFunction which takes the same parameters as your target method, to memoize values based on all parameters, or some other custom logic

    import {Memoize} from 'typescript-memoize';
    
    class MoreComplicatedFoo {
    
    	// Memoize a method with multiple parameters
    	// Memoize will remember values based on keys like: 'name;planet'
    	@Memoize((name: string, planet: string) => {
    		return name + ';' + string;
    	})
    	public getBetterGreeting(name: string, planet: string) {
    		return 'Hello, ' + name + '! Welcome to ' + planet;
    	}
    	
    	// Memoize based on some other logic
    	@Memoize(() => {
    		return new Date();
    	})
    	public memoryLeak(greeting: string) {
    		return greeting + '!!!!!';
    	}
    
    }

    We call these methods from somewhere else in our code. By now you should be getting the idea:

    let moreComplicatedFoo = new MoreComplicatedFoo();
    
    // 'Hello, Darryl! Welcome to Earth'
    let greeterVal1 = moreComplicatedFoo.getBetterGreeting('Darryl', 'Earth');
    
    // 'Hello, Darryl! Welcome to Mars'
    let greeeterVal2 = moreComplicatedFoo.getBetterGreeting('Darryl', 'Mars');
    
    // Fill up the computer with useless greetings:
    let greeting = moreComplicatedFoo.memoryLeak('Hello');

    Install

    npm i typescript-memoize

    DownloadsWeekly Downloads

    120,141

    Version

    1.0.1

    License

    MIT

    Unpacked Size

    24.7 kB

    Total Files

    9

    Last publish

    Collaborators

    • darrylhodgins