1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
'use strict';
const common = require('../common');
const assert = require('assert');
const inherits = require('util').inherits;
const errCheck = common.expectsError({
code: 'ERR_INVALID_ARG_TYPE',
type: TypeError,
message: 'The "superCtor" argument must be of type function'
});
// super constructor
function A() {
this._a = 'a';
}
A.prototype.a = function() { return this._a; };
// one level of inheritance
function B(value) {
A.call(this);
this._b = value;
}
inherits(B, A);
B.prototype.b = function() { return this._b; };
assert.strictEqual(B.super_, A);
const b = new B('b');
assert.strictEqual(b.a(), 'a');
assert.strictEqual(b.b(), 'b');
assert.strictEqual(b.constructor, B);
// two levels of inheritance
function C() {
B.call(this, 'b');
this._c = 'c';
}
inherits(C, B);
C.prototype.c = function() { return this._c; };
C.prototype.getValue = function() { return this.a() + this.b() + this.c(); };
assert.strictEqual(C.super_, B);
const c = new C();
assert.strictEqual(c.getValue(), 'abc');
assert.strictEqual(c.constructor, C);
// inherits can be called after setting prototype properties
function D() {
C.call(this);
this._d = 'd';
}
D.prototype.d = function() { return this._d; };
inherits(D, C);
assert.strictEqual(D.super_, C);
const d = new D();
assert.strictEqual(d.c(), 'c');
assert.strictEqual(d.d(), 'd');
assert.strictEqual(d.constructor, D);
// ES6 classes can inherit from a constructor function
class E {
constructor() {
D.call(this);
this._e = 'e';
}
e() { return this._e; }
}
inherits(E, D);
assert.strictEqual(E.super_, D);
const e = new E();
assert.strictEqual(e.getValue(), 'abc');
assert.strictEqual(e.d(), 'd');
assert.strictEqual(e.e(), 'e');
assert.strictEqual(e.constructor, E);
// should throw with invalid arguments
assert.throws(function() {
inherits(A, {});
}, common.expectsError({
code: 'ERR_INVALID_ARG_TYPE',
type: TypeError,
message: 'The "superCtor.prototype" property must be of type function'
})
);
assert.throws(function() {
inherits(A, null);
}, errCheck);
assert.throws(function() {
inherits(null, A);
}, common.expectsError({
code: 'ERR_INVALID_ARG_TYPE',
type: TypeError,
message: 'The "ctor" argument must be of type function'
})
);
|
