159 lines
3.2 KiB
JavaScript
159 lines
3.2 KiB
JavaScript
const { observable, computed } = require('../lib/index.js');
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describe('computed', () => {
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const add = (a, b) => a + b;
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const square = a => a * a;
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it('returns the value computed from its dependencies', () => {
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const a = observable(0);
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const b = computed(square, [a]);
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const c = computed(add, [a, b]);
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expect(b()).toEqual(0);
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expect(c()).toEqual(0);
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a(1);
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expect(b()).toEqual(1);
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expect(c()).toEqual(2);
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a(2);
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expect(b()).toEqual(4);
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expect(c()).toEqual(6);
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a(3);
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expect(b()).toEqual(9);
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expect(c()).toEqual(12);
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});
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it('only computes when called', () => {
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let runCount = 0;
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let currentValue = 1;
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const a = observable(0);
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const b = computed(
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val => {
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runCount += 1;
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expect(val).toEqual(currentValue);
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return val * val;
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},
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[a]
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);
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a(1);
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expect(runCount).toEqual(0);
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// b evaluates
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expect(b()).toEqual(1);
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expect(runCount).toEqual(1);
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// b does not evaluate
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expect(b()).toEqual(1);
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expect(runCount).toEqual(1);
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currentValue = 3;
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// b does not evaluate
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a(3);
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expect(runCount).toEqual(1);
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// b evaluates
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expect(b()).toEqual(9);
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expect(runCount).toEqual(2);
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});
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it('computes automatically when subscribed', () => {
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let runCount = 0;
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let subRunCount = 0;
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let currentValue = 1;
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const a = observable(0);
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const b = computed(
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val => {
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runCount += 1;
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expect(val).toEqual(currentValue);
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return val * val;
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},
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[a]
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);
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// b does not evaluate
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a(1);
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expect(runCount).toEqual(0);
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// b evaluates
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expect(b()).toEqual(1);
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expect(runCount).toEqual(1);
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// b does not evaluate
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expect(b()).toEqual(1);
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expect(runCount).toEqual(1);
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const cancelSubscription = b.subscribe(val => {
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subRunCount += 1;
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expect(val).toEqual(currentValue * currentValue);
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});
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currentValue = 3;
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// b evaluates
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a(3);
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expect(runCount).toEqual(2);
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expect(subRunCount).toEqual(1);
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// b does not evaluate
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expect(b()).toEqual(9);
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expect(runCount).toEqual(2);
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expect(subRunCount).toEqual(1);
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});
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it('honors cancelled subscriptions', () => {
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let runCount = 0;
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let subRunCount = 0;
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let currentValue = 1;
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const a = observable(0);
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const b = computed(
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val => {
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runCount += 1;
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expect(val).toEqual(currentValue);
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return val * val;
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},
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[a]
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);
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const cancelSubscription = b.subscribe(val => {
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subRunCount += 1;
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expect(val).toEqual(currentValue * currentValue);
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});
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const cancelSubscription2 = b.subscribe(val => {
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subRunCount += 1;
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});
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// b evaluates
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a(1);
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expect(runCount).toEqual(1);
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expect(subRunCount).toEqual(2);
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// b does not evaluate
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expect(b()).toEqual(1);
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expect(runCount).toEqual(1);
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expect(subRunCount).toEqual(2);
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expect(cancelSubscription()).toEqual(1);
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currentValue = 3;
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// b evaluates
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a(3);
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expect(runCount).toEqual(2);
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expect(subRunCount).toEqual(3);
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// b does not evaluate
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expect(b()).toEqual(9);
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expect(runCount).toEqual(2);
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expect(subRunCount).toEqual(3);
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expect(cancelSubscription2()).toEqual(0);
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});
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it('can be detached', () => {
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const a = observable(2);
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const b = computed(square, [a]);
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const c = computed(add, [a, b]);
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expect(b()).toEqual(4);
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expect(c()).toEqual(6);
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b.detach();
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a(3);
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expect(b()).toEqual(4);
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expect(c()).toEqual(7);
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});
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});
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