Reimplement Function.prototype.bind.

test/mjsunit/function-bind.js

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 11 matching lines @@
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Tests the Function.prototype.bind (ES 15.3.4.5) method.
 
 // Simple tests.
 function foo(x, y, z) {
-  return x + y + z;
+  return [this, arguments.length, x];
 }
 
+assertEquals(3, foo.length);
+
 var f = foo.bind(foo);
-assertEquals(3, f(1, 1, 1));
+assertEquals([foo, 3, 1], f(1, 2, 3));
 assertEquals(3, f.length);
 
-f = foo.bind(foo, 2);
-assertEquals(4, f(1, 1));
+f = foo.bind(foo, 1);
+assertEquals([foo, 3, 1], f(2, 3));
 assertEquals(2, f.length);
 
-f = foo.bind(foo, 2, 2);
-assertEquals(5, f(1));
+f = foo.bind(foo, 1, 2);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
-f = foo.bind(foo, 2, 2, 2);
-assertEquals(6, f());
+f = foo.bind(foo, 1, 2, 3);
+assertEquals([foo, 3, 1], f());
 assertEquals(0, f.length);
 
 // Test that length works correctly even if more than the actual number
 // of arguments are given when binding.
 f = foo.bind(foo, 1, 2, 3, 4, 5, 6, 7, 8, 9);
-assertEquals(6, f());
+assertEquals([foo, 9, 1], f());
 assertEquals(0, f.length);
 
 // Use a different bound object.
 var obj = {x: 42, y: 43};
 // Values that would normally be in "this" when calling f_bound_this.
 var x = 42;
 var y = 44;
 
 function f_bound_this(z) {
   return z + this.y - this.x;
 }
 
 assertEquals(3, f_bound_this(1))
 f = f_bound_this.bind(obj);
 assertEquals(2, f(1));
 assertEquals(1, f.length);
 
 f = f_bound_this.bind(obj, 2);
 assertEquals(3, f());
 assertEquals(0, f.length);
 
 // Test chained binds.
 
 // When only giving the thisArg, any number of binds should have
 // the same effect.
 f = foo.bind(foo);
-assertEquals(3, f(1, 1, 1));
-f = foo.bind(foo).bind(foo).bind(foo).bind(foo);
-assertEquals(3, f(1, 1, 1));
+assertEquals([foo, 3, 1], f(1, 2, 3));
+
+var not_foo = {};
+f = foo.bind(foo).bind(not_foo).bind(not_foo).bind(not_foo);
+assertEquals([foo, 3, 1], f(1, 2, 3));
 assertEquals(3, f.length);
 
 // Giving bound parameters should work at any place in the chain.
-f = foo.bind(foo, 1).bind(foo).bind(foo).bind(foo);
-assertEquals(3, f(1, 1));
+f = foo.bind(foo, 1).bind(not_foo).bind(not_foo).bind(not_foo);
+assertEquals([foo, 3, 1], f(2, 3));
 assertEquals(2, f.length);
 
-f = foo.bind(foo).bind(foo, 1).bind(foo).bind(foo);
-assertEquals(3, f(1, 1));
+f = foo.bind(foo).bind(not_foo, 1).bind(not_foo).bind(not_foo);
+assertEquals([foo, 3, 1], f(2, 3));
 assertEquals(2, f.length);
 
-f = foo.bind(foo).bind(foo).bind(foo,1 ).bind(foo);
-assertEquals(3, f(1, 1));
+f = foo.bind(foo).bind(not_foo).bind(not_foo,1 ).bind(not_foo);
+assertEquals([foo, 3, 1], f(2, 3));
 assertEquals(2, f.length);
 
-f = foo.bind(foo).bind(foo).bind(foo).bind(foo, 1);
-assertEquals(3, f(1, 1));
+f = foo.bind(foo).bind(not_foo).bind(not_foo).bind(not_foo, 1);
+assertEquals([foo, 3, 1], f(2, 3));
 assertEquals(2, f.length);
 
 // Several parameters can be given, and given in different bind invokations.

[rossberg, 2011/10/17 11:49:08]

Typo: invocations

[Lasse Reichstein, 2011/10/17 12:38:39]

Fixed.

-f = foo.bind(foo, 1, 1).bind(foo).bind(foo).bind(foo);
-assertEquals(3, f(1));
+f = foo.bind(foo, 1, 2).bind(not_foo).bind(not_foo).bind(not_foo);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
-f = foo.bind(foo).bind(foo, 1, 1).bind(foo).bind(foo);
-assertEquals(3, f(1));
+f = foo.bind(foo).bind(not_foo, 1, 2).bind(not_foo).bind(not_foo);
+assertEquals([foo, 3, 1], f(1));
 assertEquals(1, f.length);
 
-f = foo.bind(foo).bind(foo, 1, 1).bind(foo).bind(foo);
-assertEquals(3, f(1));
+f = foo.bind(foo).bind(not_foo, 1, 2).bind(not_foo).bind(not_foo);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
-f = foo.bind(foo).bind(foo).bind(foo, 1, 1).bind(foo);
-assertEquals(3, f(1));
+f = foo.bind(foo).bind(not_foo).bind(not_foo, 1, 2).bind(not_foo);
+assertEquals([foo, 3, 1], f(1));
 assertEquals(1, f.length);
 
-f = foo.bind(foo).bind(foo).bind(foo).bind(foo, 1, 1);
-assertEquals(3, f(1));
+f = foo.bind(foo).bind(not_foo).bind(not_foo).bind(not_foo, 1, 2);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
-f = foo.bind(foo, 1).bind(foo, 1).bind(foo).bind(foo);
-assertEquals(3, f(1));
+f = foo.bind(foo, 1).bind(not_foo, 2).bind(not_foo).bind(not_foo);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
-f = foo.bind(foo, 1).bind(foo).bind(foo, 1).bind(foo);
-assertEquals(3, f(1));
+f = foo.bind(foo, 1).bind(not_foo).bind(not_foo, 2).bind(not_foo);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
-f = foo.bind(foo, 1).bind(foo).bind(foo).bind(foo, 1);
-assertEquals(3, f(1));
+f = foo.bind(foo, 1).bind(not_foo).bind(not_foo).bind(not_foo, 2);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
-f = foo.bind(foo).bind(foo, 1).bind(foo).bind(foo, 1);
-assertEquals(3, f(1));
+f = foo.bind(foo).bind(not_foo, 1).bind(not_foo).bind(not_foo, 2);
+assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
 
+// The wrong number of arguments can be given to bound functions too.
+f = foo.bind(foo);
+assertEquals(3, f.length);
+assertEquals([foo, 0, undefined], f());
+assertEquals([foo, 1, 1], f(1));
+assertEquals([foo, 2, 1], f(1, 2));
+assertEquals([foo, 3, 1], f(1, 2, 3));
+assertEquals([foo, 4, 1], f(1, 2, 3, 4));
+
+f = foo.bind(foo, 1);
+assertEquals(2, f.length);
+assertEquals([foo, 1, 1], f());
+assertEquals([foo, 2, 1], f(2));
+assertEquals([foo, 3, 1], f(2, 3));
+assertEquals([foo, 4, 1], f(2, 3, 4));
+
+f = foo.bind(foo, 1, 2);
+assertEquals(1, f.length);
+assertEquals([foo, 2, 1], f());
+assertEquals([foo, 3, 1], f(3));
+assertEquals([foo, 4, 1], f(3, 4));
+
+f = foo.bind(foo, 1, 2, 3);
+assertEquals(0, f.length);
+assertEquals([foo, 3, 1], f());
+assertEquals([foo, 4, 1], f(4));
+
+f = foo.bind(foo, 1, 2, 3, 4);
+assertEquals(0, f.length);
+assertEquals([foo, 4, 1], f());
+
 // Test constructor calls.
 
 function bar(x, y, z) {
   this.x = x;
   this.y = y;
   this.z = z;
 }
 
 f = bar.bind(bar);
 var obj2 = new f(1,2,3);
@@ skipping 14 matching lines @@
 assertEquals(3, obj2.z);
 
 f = bar.bind(bar, 1, 2, 3);
 obj2 = new f();
 assertEquals(1, obj2.x);
 assertEquals(2, obj2.y);
 assertEquals(3, obj2.z);
 
 
 // Test bind chains when used as a constructor.
-
 f = bar.bind(bar, 1).bind(bar, 2).bind(bar, 3);
 obj2 = new f();
 assertEquals(1, obj2.x);
 assertEquals(2, obj2.y);
 assertEquals(3, obj2.z);
 
-// Test instanceof obj2 is bar, not f.
+// Test obj2 is instanceof both bar and f.
 assertTrue(obj2 instanceof bar);
-assertFalse(obj2 instanceof f);
+assertTrue(obj2 instanceof f);
+
+// This-args are not relevant to instanceof.
+f = bar.bind(foo.prototype, 1).
+    bind(String.prototype, 2).
+    bind(Function.prototype, 3);
+var obj3 = new f();
+assertTrue(obj3 instanceof bar);
+assertTrue(obj3 instanceof f);
+assertFalse(obj3 instanceof foo);
+assertFalse(obj3 instanceof Function);
+assertFalse(obj3 instanceof String);
+
+// thisArg is converted to object.
+f = foo.bind(undefined);
+assertEquals([this, 0, undefined], f());
+
+f = foo.bind(null);
+assertEquals([this, 0, undefined], f());
+
+f = foo.bind(42);
+assertEquals([Object(42), 0, undefined], f());
+
+f = foo.bind("foo");
+assertEquals([Object("foo"), 0, undefined], f());
+
+f = foo.bind(true);
+assertEquals([Object(true), 0, undefined], f());
+
+// Strict functions don't convert thisArg.
+function soo(x, y, z) {
+  "use strict";
+  return [this, arguments.length, x];
+}
+
+var s = soo.bind(undefined);
+assertEquals([undefined, 0, undefined], s());
+
+s = soo.bind(null);
+assertEquals([null, 0, undefined], s());
+
+s = soo.bind(42);
+assertEquals([42, 0, undefined], s());
+
+s = soo.bind("foo");
+assertEquals(["foo", 0, undefined], s());
+
+s = soo.bind(true);
+assertEquals([true, 0, undefined], s());