jcs.org
Serenity Operating System
1test("single default parameter", () => {
2 function func(a = 6) {
3 return typeof a;
4 }
5
6 const arrowFunc = (a = 6) => typeof a;
7
8 expect(func()).toBe("number");
9 expect(func(5)).toBe("number");
10 expect(func(undefined)).toBe("number");
11 expect(func(false)).toBe("boolean");
12 expect(func(null)).toBe("object");
13 expect(func({})).toBe("object");
14
15 expect(arrowFunc()).toBe("number");
16 expect(arrowFunc(5)).toBe("number");
17 expect(arrowFunc(undefined)).toBe("number");
18 expect(arrowFunc(false)).toBe("boolean");
19 expect(arrowFunc(null)).toBe("object");
20 expect(arrowFunc({})).toBe("object");
21});
22
23test("two parameters, second one is default", () => {
24 function func(a, b = 1) {
25 return a + b;
26 }
27
28 const arrowFunc = (a, b = 1) => a + b;
29
30 expect(func(4, 5)).toBe(9);
31 expect(func(4)).toBe(5);
32 expect(func(4, undefined)).toBe(5);
33 expect(func()).toBeNaN();
34
35 expect(arrowFunc(4, 5)).toBe(9);
36 expect(arrowFunc(4)).toBe(5);
37 expect(arrowFunc(4, undefined)).toBe(5);
38 expect(arrowFunc()).toBeNaN();
39});
40
41test("two parameters, first one is default", () => {
42 function func(a = 5, b) {
43 return a + b;
44 }
45
46 const arrowFunc = (a = 5, b) => a + b;
47
48 expect(func(4, 5)).toBe(9);
49 expect(func(undefined, 4)).toBe(9);
50 expect(func()).toBeNaN();
51
52 expect(arrowFunc(4, 5)).toBe(9);
53 expect(arrowFunc(undefined, 4)).toBe(9);
54 expect(arrowFunc()).toBeNaN();
55});
56
57test("default parameter references a previous parameter", () => {
58 function func(a, b = a) {
59 return a + b;
60 }
61
62 const arrowFunc = (a, b = a) => a + b;
63
64 expect(func(4, 5)).toBe(9);
65 expect(func(4)).toBe(8);
66 expect(func("hf")).toBe("hfhf");
67 expect(func(true)).toBe(2);
68 expect(func()).toBeNaN();
69
70 expect(arrowFunc(4, 5)).toBe(9);
71 expect(arrowFunc(4)).toBe(8);
72 expect(arrowFunc("hf")).toBe("hfhf");
73 expect(arrowFunc(true)).toBe(2);
74 expect(arrowFunc()).toBeNaN();
75});
76
77test("parameter with a function default value", () => {
78 function func(
79 a = function () {
80 return 5;
81 }
82 ) {
83 return a();
84 }
85
86 const arrowFunc = (
87 a = function () {
88 return 5;
89 }
90 ) => a();
91
92 expect(func()).toBe(5);
93 expect(
94 func(function () {
95 return 10;
96 })
97 ).toBe(10);
98 expect(func(() => 10)).toBe(10);
99
100 expect(arrowFunc()).toBe(5);
101 expect(
102 arrowFunc(function () {
103 return 10;
104 })
105 ).toBe(10);
106 expect(arrowFunc(() => 10)).toBe(10);
107});
108
109test("parameter with an arrow function default value", () => {
110 function func(a = () => 5) {
111 return a();
112 }
113
114 const arrowFunc = (a = () => 5) => a();
115
116 expect(func()).toBe(5);
117 expect(
118 func(function () {
119 return 10;
120 })
121 ).toBe(10);
122 expect(func(() => 10)).toBe(10);
123 expect(arrowFunc()).toBe(5);
124 expect(
125 arrowFunc(function () {
126 return 10;
127 })
128 ).toBe(10);
129 expect(arrowFunc(() => 10)).toBe(10);
130});
131
132test("parameter with an object default value", () => {
133 function func(a = { foo: "bar" }) {
134 return a.foo;
135 }
136
137 const arrowFunc = (a = { foo: "bar" }) => a.foo;
138
139 expect(func()).toBe("bar");
140 expect(func({ foo: "baz" })).toBe("baz");
141 expect(arrowFunc()).toBe("bar");
142 expect(arrowFunc({ foo: "baz" })).toBe("baz");
143});