xstream/extra/dropRepeats.js

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

"use strict";
var core_1 = require('../core');
var empty = {};
var DropRepeatsOperator = (function () {
    function DropRepeatsOperator(fn, ins) {
        this.fn = fn;
        this.ins = ins;
        this.type = 'dropRepeats';
        this.out = null;
        this.v = empty;
    }
    DropRepeatsOperator.prototype._start = function (out) {
        this.out = out;
        this.ins._add(this);
    };
    DropRepeatsOperator.prototype._stop = function () {
        this.ins._remove(this);
        this.out = null;
        this.v = empty;
    };
    DropRepeatsOperator.prototype.isEq = function (x, y) {
        return this.fn ? this.fn(x, y) : x === y;
    };
    DropRepeatsOperator.prototype._n = function (t) {
        var u = this.out;
        if (!u)
            return;
        var v = this.v;
        if (v !== empty && this.isEq(t, v))
            return;
        this.v = t;
        u._n(t);
    };
    DropRepeatsOperator.prototype._e = function (err) {
        var u = this.out;
        if (!u)
            return;
        u._e(err);
    };
    DropRepeatsOperator.prototype._c = function () {
        var u = this.out;
        if (!u)
            return;
        u._c();
    };
    return DropRepeatsOperator;
}());
exports.DropRepeatsOperator = DropRepeatsOperator;
/**
 * Drops consecutive duplicate values in a stream.
 *
 * Marble diagram:
 *
 * ```text
 * --1--2--1--1--1--2--3--4--3--3|
 *     dropRepeats
 * --1--2--1--------2--3--4--3---|
 * ```
 *
 * Example:
 *
 * ```js
 * import dropRepeats from 'xstream/extra/dropRepeats'
 *
 * const stream = xs.of(1, 2, 1, 1, 1, 2, 3, 4, 3, 3)
 *   .compose(dropRepeats())
 *
 * stream.addListener({
 *   next: i => console.log(i),
 *   error: err => console.error(err),
 *   complete: () => console.log('completed')
 * })
 * ```
 *
 * ```text
 * > 1
 * > 2
 * > 1
 * > 2
 * > 3
 * > 4
 * > 3
 * > completed
 * ```
 *
 * Example with a custom isEqual function:
 *
 * ```js
 * import dropRepeats from 'xstream/extra/dropRepeats'
 *
 * const stream = xs.of('a', 'b', 'a', 'A', 'B', 'b')
 *   .compose(dropRepeats((x, y) => x.toLowerCase() === y.toLowerCase()))
 *
 * stream.addListener({
 *   next: i => console.log(i),
 *   error: err => console.error(err),
 *   complete: () => console.log('completed')
 * })
 * ```
 *
 * ```text
 * > a
 * > b
 * > a
 * > B
 * > completed
 * ```
 *
 * @param {Function} isEqual An optional function of type
 * `(x: T, y: T) => boolean` that takes an event from the input stream and
 * checks if it is equal to previous event, by returning a boolean.
 * @return {Stream}
 */
function dropRepeats(isEqual) {
    if (isEqual === void 0) { isEqual = null; }
    return function dropRepeatsOperator(ins) {
        return new core_1.Stream(new DropRepeatsOperator(isEqual, ins));
    };
}
Object.defineProperty(exports, "__esModule", { value: true });
exports.default = dropRepeats;
//# sourceMappingURL=dropRepeats.js.map