77 lines
2.4 KiB
JavaScript
77 lines
2.4 KiB
JavaScript
test("length is 2", () => {
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expect(Object.groupBy).toHaveLength(2);
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});
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describe("errors", () => {
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test("callback must be a function", () => {
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expect(() => {
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Object.groupBy([], undefined);
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}).toThrowWithMessage(TypeError, "undefined is not a function");
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});
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test("null or undefined items value", () => {
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expect(() => {
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Object.groupBy();
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}).toThrowWithMessage(TypeError, "undefined cannot be converted to an object");
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expect(() => {
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Object.groupBy(undefined);
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}).toThrowWithMessage(TypeError, "undefined cannot be converted to an object");
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expect(() => {
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Object.groupBy(null);
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}).toThrowWithMessage(TypeError, "null cannot be converted to an object");
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});
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});
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describe("normal behavior", () => {
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test("basic functionality", () => {
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const array = [1, 2, 3, 4, 5, 6];
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const visited = [];
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const firstResult = Object.groupBy(array, value => {
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visited.push(value);
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return value % 2 === 0;
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});
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expect(visited).toEqual([1, 2, 3, 4, 5, 6]);
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expect(firstResult.true).toEqual([2, 4, 6]);
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expect(firstResult.false).toEqual([1, 3, 5]);
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const firstKeys = Object.keys(firstResult);
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expect(firstKeys).toHaveLength(2);
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expect(firstKeys[0]).toBe("false");
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expect(firstKeys[1]).toBe("true");
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const secondResult = Object.groupBy(array, (_, index) => {
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return index < array.length / 2;
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});
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expect(secondResult.true).toEqual([1, 2, 3]);
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expect(secondResult.false).toEqual([4, 5, 6]);
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const secondKeys = Object.keys(secondResult);
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expect(secondKeys).toHaveLength(2);
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expect(secondKeys[0]).toBe("true");
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expect(secondKeys[1]).toBe("false");
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});
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test("never calls callback with empty array", () => {
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var callbackCalled = 0;
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expect(
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Object.groupBy([], () => {
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callbackCalled++;
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})
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).toEqual({});
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expect(callbackCalled).toBe(0);
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});
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test("calls callback once for every item", () => {
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var callbackCalled = 0;
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const result = Object.groupBy([1, 2, 3], () => {
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callbackCalled++;
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});
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expect(result.undefined).toEqual([1, 2, 3]);
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expect(callbackCalled).toBe(3);
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});
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});
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