xstream/extra/pairwise.js

An extremely intuitive, small, and fast functional reactive stream library for JavaScript

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var index_1 = require("../index");
var PairwiseOperator = /** @class */ (function () {
    function PairwiseOperator(ins) {
        this.ins = ins;
        this.type = 'pairwise';
        this.val = null;
        this.has = false;
        this.out = null;
    }
    PairwiseOperator.prototype._start = function (out) {
        this.out = out;
        this.ins._add(this);
    };
    PairwiseOperator.prototype._stop = function () {
        this.ins._remove(this);
        this.has = false;
        this.out = null;
        this.val = null;
    };
    PairwiseOperator.prototype._n = function (t) {
        var u = this.out;
        if (!u)
            return;
        if (this.has) {
            var prev = this.val;
            this.val = t;
            u._n([prev, t]);
        }
        else {
            this.val = t;
            this.has = true;
        }
    };
    PairwiseOperator.prototype._e = function (err) {
        var u = this.out;
        if (!u)
            return;
        u._e(err);
    };
    PairwiseOperator.prototype._c = function () {
        var u = this.out;
        if (!u)
            return;
        u._c();
    };
    return PairwiseOperator;
}());
/**
 * Group consecutive pairs of events as arrays. Each array has two items.
 *
 * Marble diagram:
 *
 * ```text
 * ---1---2-----3-----4-----5--------|
 *       pairwise
 * -------[1,2]-[2,3]-[3,4]-[4,5]----|
 * ```
 *
 * Example:
 *
 * ```js
 * import pairwise from 'xstream/extra/pairwise'
 *
 * const stream = xs.of(1, 2, 3, 4, 5, 6).compose(pairwise)
 *
 * stream.addListener({
 *   next: i => console.log(i),
 *   error: err => console.error(err),
 *   complete: () => console.log('completed')
 * })
 * ```
 *
 * ```text
 * > [1,2]
 * > [2,3]
 * > [3,4]
 * > [4,5]
 * > [5,6]
 * > completed
 * ```
 *
 * @return {Stream}
 */
function pairwise(ins) {
    return new index_1.Stream(new PairwiseOperator(ins));
}
exports.default = pairwise;
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