function-bind.js revision 50ef84f5fad2def87d3fbc737bec4a32711fdef4 
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27
28// Tests the Function.prototype.bind (ES 15.3.4.5) method.
29
30// Simple tests.
31function foo(x, y, z) {
32  return x + y + z;
33}
34
35var f = foo.bind(foo);
36assertEquals(3, f(1, 1, 1));
37assertEquals(3, f.length);
38
39f = foo.bind(foo, 2);
40assertEquals(4, f(1, 1));
41assertEquals(2, f.length);
42
43f = foo.bind(foo, 2, 2);
44assertEquals(5, f(1));
45assertEquals(1, f.length);
46
47f = foo.bind(foo, 2, 2, 2);
48assertEquals(6, f());
49assertEquals(0, f.length);
50
51// Test that length works correctly even if more than the actual number
52// of arguments are given when binding.
53f = foo.bind(foo, 1, 2, 3, 4, 5, 6, 7, 8, 9);
54assertEquals(6, f());
55assertEquals(0, f.length);
56
57// Use a different bound object.
58var obj = {x: 42, y: 43};
59// Values that would normally be in "this" when calling f_bound_this.
60var x = 42;
61var y = 44;
62
63function f_bound_this(z) {
64  return z + this.y - this.x;
65}
66
67assertEquals(3, f_bound_this(1))
68f = f_bound_this.bind(obj);
69assertEquals(2, f(1));
70assertEquals(1, f.length);
71
72f = f_bound_this.bind(obj, 2);
73assertEquals(3, f());
74assertEquals(0, f.length);
75
76// Test chained binds.
77
78// When only giving the thisArg, any number of binds should have
79// the same effect.
80f = foo.bind(foo);
81assertEquals(3, f(1, 1, 1));
82f = foo.bind(foo).bind(foo).bind(foo).bind(foo);
83assertEquals(3, f(1, 1, 1));
84assertEquals(3, f.length);
85
86// Giving bound parameters should work at any place in the chain.
87f = foo.bind(foo, 1).bind(foo).bind(foo).bind(foo);
88assertEquals(3, f(1, 1));
89assertEquals(2, f.length);
90
91f = foo.bind(foo).bind(foo, 1).bind(foo).bind(foo);
92assertEquals(3, f(1, 1));
93assertEquals(2, f.length);
94
95f = foo.bind(foo).bind(foo).bind(foo,1 ).bind(foo);
96assertEquals(3, f(1, 1));
97assertEquals(2, f.length);
98
99f = foo.bind(foo).bind(foo).bind(foo).bind(foo, 1);
100assertEquals(3, f(1, 1));
101assertEquals(2, f.length);
102
103// Several parameters can be given, and given in different bind invokations.
104f = foo.bind(foo, 1, 1).bind(foo).bind(foo).bind(foo);
105assertEquals(3, f(1));
106assertEquals(1, f.length);
107
108f = foo.bind(foo).bind(foo, 1, 1).bind(foo).bind(foo);
109assertEquals(3, f(1));
110assertEquals(1, f.length);
111
112f = foo.bind(foo).bind(foo, 1, 1).bind(foo).bind(foo);
113assertEquals(3, f(1));
114assertEquals(1, f.length);
115
116f = foo.bind(foo).bind(foo).bind(foo, 1, 1).bind(foo);
117assertEquals(3, f(1));
118assertEquals(1, f.length);
119
120f = foo.bind(foo).bind(foo).bind(foo).bind(foo, 1, 1);
121assertEquals(3, f(1));
122assertEquals(1, f.length);
123
124f = foo.bind(foo, 1).bind(foo, 1).bind(foo).bind(foo);
125assertEquals(3, f(1));
126assertEquals(1, f.length);
127
128f = foo.bind(foo, 1).bind(foo).bind(foo, 1).bind(foo);
129assertEquals(3, f(1));
130assertEquals(1, f.length);
131
132f = foo.bind(foo, 1).bind(foo).bind(foo).bind(foo, 1);
133assertEquals(3, f(1));
134assertEquals(1, f.length);
135
136f = foo.bind(foo).bind(foo, 1).bind(foo).bind(foo, 1);
137assertEquals(3, f(1));
138assertEquals(1, f.length);
139
140// Test constructor calls.
141
142function bar(x, y, z) {
143  this.x = x;
144  this.y = y;
145  this.z = z;
146}
147
148f = bar.bind(bar);
149var obj2 = new f(1,2,3);
150assertEquals(1, obj2.x);
151assertEquals(2, obj2.y);
152assertEquals(3, obj2.z);
153
154f = bar.bind(bar, 1);
155obj2 = new f(2,3);
156assertEquals(1, obj2.x);
157assertEquals(2, obj2.y);
158assertEquals(3, obj2.z);
159
160f = bar.bind(bar, 1, 2);
161obj2 = new f(3);
162assertEquals(1, obj2.x);
163assertEquals(2, obj2.y);
164assertEquals(3, obj2.z);
165
166f = bar.bind(bar, 1, 2, 3);
167obj2 = new f();
168assertEquals(1, obj2.x);
169assertEquals(2, obj2.y);
170assertEquals(3, obj2.z);
171
172
173// Test bind chains when used as a constructor.
174
175f = bar.bind(bar, 1).bind(bar, 2).bind(bar, 3);
176obj2 = new f();
177assertEquals(1, obj2.x);
178assertEquals(2, obj2.y);
179assertEquals(3, obj2.z);
180
181// Test instanceof obj2 is bar, not f.
182assertTrue(obj2 instanceof bar);
183assertFalse(obj2 instanceof f);
184
185