demystifying prototypes
TRANSCRIPT
typesDemystifyingProto...........
types
undefined numbernull
boolean objectstring
undefined numbernull
boolean objectstring
b.name
b[“name”]
“a” in b
for (var i in b) …
b.hasOwnProperty(“a”)
b instanceof d
function f() {};
f();new f;
function
function f() {};
f();new f;
function
function f() {};
f();new f;
function
ObjectNumberStringBooleanFunctionArrayRegExpDate
A
function A() {};
A
function A() {};
constructor: A
A
b
function A() {};
constructor: A
var b = new A;
A
b
x: 1
function A() {};
constructor: A
var b = new A;A.prototype.x = 1;
A
b
x: 1
y: 2
function A() {};
constructor: A
var b = new A;A.prototype.x = 1;b.y = 2;
A
bc
x: 1
y: 2
function A() {};
constructor: A
var b = new A;A.prototype.x = 1;b.y = 2;var c = new A;
A
bc
x: 1
y: 2
function A() {};
constructor: A
var b = new A;A.prototype.x = 1;b.y = 2;var c = new A;A.prototype = {v: 1, w: 2};
A
bc
x: 1
y: 2
v: 1w: 2
function A() {};
constructor: A
var b = new A;A.prototype.x = 1;b.y = 2;var c = new A;A.prototype = {v: 1, w: 2};
A
bc
x: 1
y: 2d
v: 1w: 2
function A() {};
constructor: A
var b = new A;A.prototype.x = 1;b.y = 2;var c = new A;A.prototype = {v: 1, w: 2};var d = new A;
A P
bc
x: 1
y: 2d
v: 1w: 2
constructor: A
P.hasOwnProperty(“constructor”)“constructor” in cfor (var i in P) alert(i);c.constructorc instanceof Ad instanceof Ad.constructor
null
d
A
Object
c
function A() {};function B() {};B.prototype = new A;var d = new B;
null
d
A
Object
B
null
d
A
Object
B
function A() {…};function B() {};var Z = function () {};Z.prototype = A.prototype;B.prototype = new Z;var d = new B;
null
d
A
Object
B
function A() {…};function B() {};var Z = function () {};Z.prototype = A.prototype;B.prototype = new Z;var d = new B;
Z
goog.inherits = function(childCtor, parentCtor) { /** @constructor */ function tempCtor() {}; tempCtor.prototype = parentCtor.prototype; childCtor.superClass_ = parentCtor.prototype; childCtor.prototype = new tempCtor(); childCtor.prototype.constructor = childCtor;};
exports.inherits = function(ctor, superCtor) { ctor.super_ = superCtor; ctor.prototype = Object.create(superCtor.prototype, { constructor: { value: ctor, enumerable: false } });};
null
A
Function
Object
null
A
Function
Object
Function.constructor === Function
JavaScript Paradox
