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The drawback of this solution is its verbosity; The call to Circle.
prototype.area is long and couples Sphere very tightly to Circle . To miti-
gate this, Listing 7.33 makes the inherit function set up a “super” link for us.
Listing 7.33 Expecting the _ super link to refer to the prototype
"test should set up link to super": function () {
var SubFn = function () {};
var SuperFn = function () {};
assertEquals(SuperFn.prototype, SubFn.prototype._super);
Note the leading underscore. ECMA-262 defines super as a reserved word
intended for future use, so we best not use it. The implementation in Listing 7.34
is still straightforward.
Listing 7.34 Implementing a link to the prototype
if (!Function.prototype.inherit) {
(function () {
function F() {}
Function.prototype.inherit = function (superFn) {
F.prototype = superFn.prototype;
this.prototype = new F();
this.prototype.constructor = this;
this.prototype._super = superFn.prototype;
Using this new property, Listing 7.35 simplifies Sphere.prototype.area .
Listing 7.35 Calling a method on the prototype chain
Sphere.prototype.area = function () {
return 4 *;
}; The _ super Method
Although I would definitely not recommend it, someone serious about emulating
classical inheritance in JavaScript would probably prefer _ super to be a method
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