XStream distinct

README.md

xstream distinct

A function to use with xstream#compose to filter repeated events

Example

stream
  .compose(distinct((a, b) => a.id === b.id)
  .map(uniqueValue => { //... })
  

distinct.js

/**
 * A Function to use with xstream$XStream#compose
 * filters the stream to allow allow new events.
 * Uses a compareFn to check if the event is new or not
 * @param {Function} compareFn - a function that receives two elements and compares return whether they are equal or not
 */
const distinct = (compareFn) => {
  const buffer = [];
  return (stream) => {
    return stream
      .filter(val => {
        const found = buffer.find(b => compareFn(val, b))
        if (found) return false;
        buffer.push(val);
        return true;
      });
  };
};

export default distinct;