@reactivex/rxjs/spec-js/operators/elementAt-spec.js

Reactive Extensions for modern JavaScript

"use strict";
var chai_1 = require('chai');
var Rx = require('../../dist/cjs/Rx');
var Observable = Rx.Observable;
/** @test {elementAt} */
describe('Observable.prototype.elementAt', function () {
    asDiagram('elementAt(2)')('should return last element by zero-based index', function () {
        var source = hot('--a--b--c-d---|');
        var subs = '^       !      ';
        var expected = '--------(c|)   ';
        expectObservable(source.elementAt(2)).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should return first element by zero-based index', function () {
        var source = hot('--a--b--c--|');
        var subs = '^ !';
        var expected = '--(a|)';
        expectObservable(source.elementAt(0)).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should return non-first element by zero-based index', function () {
        var source = hot('--a--b--c--d--e--f--|');
        var subs = '^          !';
        var expected = '-----------(d|)';
        expectObservable(source.elementAt(3)).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should return last element by zero-based index', function () {
        var source = hot('--a--b--c--|');
        var subs = '^       !';
        var expected = '--------(c|)';
        expectObservable(source.elementAt(2)).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should raise error if source is Empty Observable', function () {
        var source = cold('|');
        var subs = '(^!)';
        var expected = '#';
        expectObservable(source.elementAt(0)).toBe(expected, undefined, new Rx.ArgumentOutOfRangeError());
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should propagate error if source is Throw Observable', function () {
        var source = cold('#');
        var subs = '(^!)';
        var expected = '#';
        expectObservable(source.elementAt(0)).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should return Never if source is Never Observable', function () {
        var source = cold('-');
        var subs = '^';
        var expected = '-';
        expectObservable(source.elementAt(0)).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should allow unsubscribing early and explicitly', function () {
        var source = hot('--a--b--c--|');
        var subs = '^     !     ';
        var expected = '-------     ';
        var unsub = '      !     ';
        var result = source.elementAt(2);
        expectObservable(result, unsub).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should not break unsubscription chains when result Observable is unsubscribed', function () {
        var source = hot('--a--b--c--|');
        var subs = '^     !     ';
        var expected = '-------     ';
        var unsub = '      !     ';
        var result = source
            .mergeMap(function (x) { return Observable.of(x); })
            .elementAt(2)
            .mergeMap(function (x) { return Observable.of(x); });
        expectObservable(result, unsub).toBe(expected);
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should throw if index is smaller than zero', function () {
        chai_1.expect(function () { Observable.range(0, 10).elementAt(-1); })
            .to.throw(Rx.ArgumentOutOfRangeError);
    });
    it('should raise error if index is out of range but does not have default value', function () {
        var source = hot('--a--|');
        var subs = '^    !';
        var expected = '-----#';
        expectObservable(source.elementAt(3))
            .toBe(expected, null, new Rx.ArgumentOutOfRangeError());
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
    it('should return default value if index is out of range', function () {
        var source = hot('--a--|');
        var subs = '^    !';
        var expected = '-----(x|)';
        var defaultValue = '42';
        expectObservable(source.elementAt(3, defaultValue)).toBe(expected, { x: defaultValue });
        expectSubscriptions(source.subscriptions).toBe(subs);
    });
});
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