Retrieve data from a JavaScript generator-stream by applying a filter to the values

Question

Retrieve data from a JavaScript generator-stream by applying a filter to the values

After watching a thought-provoking video on computerphile, I was inspired to try my hand at implementing the sieve algorithm using JavaScript generators. While I have experience with JavaScript, working directly with generators is a new challenge for me.

Here's my current progress:

function* nextNaturalNumber(n) {
    yield n;
    yield* nextNaturalNumber(n + 1);
}   

function* sieve(n) {
    let count = 0;
    let g = nextNaturalNumber(2);
    while (count++ < n) {
        const possiblePrime = g.next().value;
        yield possiblePrime;
        // Here's where I'm encountering an obstacle:
        // How can I filter out values from the nextNaturalNumber-generator stream that are not divisible by 2?
    }
}

// Display the first 10 prime numbers
for (const prime of sieve(10)) {
    console.log(prime);
}

The code-comment indicates my struggle with filtering out values in the generator stream that are not divisible by 2 and achieving the "sieve" operation. Is there a straightforward way to accomplish this task in JavaScript, similar to how it's done in Python with

yield from sieve(i for i in s if i%n !=0)

?

javascript generator

Answer 1

Answer №1

Regrettably, the Javascript language lacks robust iterator operations. One workaround is to create a filter function that iterates through the elements and returns only those that meet certain criteria:

function* generateSequence(n) {
    // Using iteration instead of recursion to prevent stack overflow
    while(true) {
        yield n;
        n++;
    }
}   

function* filterIterator(iterator, condition) {
    for (const item of iterator) {
        if (condition(item)) {
            yield item;
        }
    }
}

function* primeSieve(limit) {
    let count = 0;
    let sequence = generateSequence(2);
    while (count++ < limit) {
        const possiblePrime = sequence.next().value;
        yield possiblePrime;
        sequence = filterIterator(sequence, value => value % possiblePrime !== 0);
    }
}

// Display the first 10 prime numbers
for (const primeNumber of primeSieve(10)) {
    console.log(primeNumber);
}

Answer 2

Regrettably, the Javascript language lacks robust iterator operations. One workaround is to create a filter function that iterates through the elements and returns only those that meet certain criteria:

function* generateSequence(n) {
    // Using iteration instead of recursion to prevent stack overflow
    while(true) {
        yield n;
        n++;
    }
}   

function* filterIterator(iterator, condition) {
    for (const item of iterator) {
        if (condition(item)) {
            yield item;
        }
    }
}

function* primeSieve(limit) {
    let count = 0;
    let sequence = generateSequence(2);
    while (count++ < limit) {
        const possiblePrime = sequence.next().value;
        yield possiblePrime;
        sequence = filterIterator(sequence, value => value % possiblePrime !== 0);
    }
}

// Display the first 10 prime numbers
for (const primeNumber of primeSieve(10)) {
    console.log(primeNumber);
}

Answer 3

Answer №2

Utilize the following code snippet to extract only odd values from your stream:

do {
    val = g.next().value;
} while (!(val%2));

Feel free to experiment with this functionality in your own code:

function* nextNaturalNumber(n) {
    yield n;
    yield* nextNaturalNumber(n + 1);
}   

function* sieve(n) {
    let count = 0;
    let g = nextNaturalNumber(2);
    while (count++ < n) {
       let val;
       do {
             val = g.next().value;
        } while (!(val%2));
        
        const possiblePrime=val;
        yield possiblePrime;
    }
}

// display the first 10 prime numbers
for (const prime of sieve(10)) {
    console.log(prime);
}

Answer 4

Utilize the following code snippet to extract only odd values from your stream:

do {
    val = g.next().value;
} while (!(val%2));

Feel free to experiment with this functionality in your own code:

function* nextNaturalNumber(n) {
    yield n;
    yield* nextNaturalNumber(n + 1);
}   

function* sieve(n) {
    let count = 0;
    let g = nextNaturalNumber(2);
    while (count++ < n) {
       let val;
       do {
             val = g.next().value;
        } while (!(val%2));
        
        const possiblePrime=val;
        yield possiblePrime;
    }
}

// display the first 10 prime numbers
for (const prime of sieve(10)) {
    console.log(prime);
}

Answer 5

Answer №3

It concerns me that you may be leaning towards Pythonic coding in JavaScript, which might not always be the best approach. JavaScript favors explicit declaration of variables over hiding them in the stack like Python does. Consider this alternative:

//
// To iterate through natural numbers...
//
function* nextNaturalNumber(n) {
    while(true) {
        yield n;
        n++;
    }
}   

function* sieve() {
    //
    // Keep track of previously seen primes
    //
    let previousPrimes = [];
    for (const possiblePrime of nextNaturalNumber(2)) {
        //
        // Check if number is divisible by any previous prime
        //
        if (!previousPrimes.find((test) => (possiblePrime % test === 0))) {
            //
            // Return prime and add it to list of seen primes
            //
            yield possiblePrime;
            previousPrimes.push(possiblePrime);
        }
    }
}

let generator = sieve();
for(let i = 0; i < 10; i++) {
    console.log(generator.next().value);
}

Answer 6

It concerns me that you may be leaning towards Pythonic coding in JavaScript, which might not always be the best approach. JavaScript favors explicit declaration of variables over hiding them in the stack like Python does. Consider this alternative:

//
// To iterate through natural numbers...
//
function* nextNaturalNumber(n) {
    while(true) {
        yield n;
        n++;
    }
}   

function* sieve() {
    //
    // Keep track of previously seen primes
    //
    let previousPrimes = [];
    for (const possiblePrime of nextNaturalNumber(2)) {
        //
        // Check if number is divisible by any previous prime
        //
        if (!previousPrimes.find((test) => (possiblePrime % test === 0))) {
            //
            // Return prime and add it to list of seen primes
            //
            yield possiblePrime;
            previousPrimes.push(possiblePrime);
        }
    }
}

let generator = sieve();
for(let i = 0; i < 10; i++) {
    console.log(generator.next().value);
}

Retrieve data from a JavaScript generator-stream by applying a filter to the values

Answer №1

Answer №2

Answer №3

Similar questions

Navigate through the DOM to return an image

How to use jQuery to update the href attribute of a parent link

The Vue.js transition feature seems to be malfunctioning when trying to display a modal

JavaScript function is not being invoked when receiving PHP arguments

Sharing Angular 4 components in my project - collaboration at its finest

Enhancing Website Interactivity with PHP, AJAX, and

Loading data from external URLs using AJAX and JSON

Processing JSON Serialization from Controller to AJAX Response

Angular directive: Exploring the disparities between controller scope and link function scope

Fade out a GLTF model in an A-frame after a short period of time

Is it possible to utilize router.push within Redux thunk? Is this considered a beneficial approach?

Enhance the appearance of your custom Component in React Native by applying styles to Styled Components

Learn the technique of rotating a line around its endpoint using DragControls in three.js

Arranging information within an ExpansionPanelSummary component in React Material-UI

Ajax is functional, however the server is not responding

Placing an eye icon on the password input field for optimal visibility and positioning

Is there a way to program custom key assignments for my calculator using JavaScript?

Passing an ID via Link to retrieve data with getServerSideProps in Next.js

What is the best way to trigger a refresh of a cached CSS file on a JSP website, without using PHP?

Sending data from JavaScript to Jade templatesIs this alright?