Finding pairs in a stream of data using windowing

index.js

require("./array.js");
const { reduce, reduced } = require("./reduce.js");
const { map, dropWhile, dedupe, window, comp } = require("./transducers.js");
const { into } = require("./into.js");


function pair_items(items){
    items = into([], dropWhile(x => x.hasOwnProperty("pair_id")), items);
    var first = items[0];
    items.shift();
    return reduce(function(i, next_item){
        if(i.id === next_item.pair_id){
            return reduced([i, next_item]);
        }
        return i;
    }, first, items);
}



const process = comp(window(3), map(pair_items), dedupe());


console.log(into([], process, [{id : 0}, {id:1, pair_id: 0}, {id:2}, {id:3}, {id:4}, {id:5, pair_id: 4}]));