Extensions--About dynamic prototypes (JavaScript Advanced Programming) (1/3)

The reason why the inheritance mechanism cannot be dynamic is: The uniqueness of the prototype object. Instance code:
Copy code code as follows:

function A (i) {
THIS.A = i;
if (typeof a._init = = ' undefined ') {
A.prototype.func = function () {
return 0;
}
A._init = 1;
}
}
function Suba (j) {
A.call (this, 1);
THIS.J = j;
if (typeof suba._init = = ' undefined ') {
Suba.prototype = new A ();
Suba.prototype.func_sub = function () {
return ++j;
}
Suba._init = 1;
}
}
var sub_a = new Suba (1);
Alert (Sub_a.func_sub ()); Error:sub_a.func_sub is not a function

Nicholas explained that before the code was run, the object had been instantiated and contacted with prototype, and the current substitution of the prototype object would not have any effect on it, that is, the current replacement would not be accessible, and only instances of future objects would reflect that change. The first instance object will be incorrect. But the second and subsequent subclass instances are fine.

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