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101 lines
2.2 KiB
101 lines
2.2 KiB
'use strict';
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const common = require('../common');
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const assert = require('assert');
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const inherits = require('util').inherits;
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const errCheck = common.expectsError({
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code: 'ERR_INVALID_ARG_TYPE',
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type: TypeError,
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message: 'The "superCtor" argument must be of type function'
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});
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// super constructor
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function A() {
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this._a = 'a';
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}
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A.prototype.a = function() { return this._a; };
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// one level of inheritance
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function B(value) {
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A.call(this);
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this._b = value;
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}
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inherits(B, A);
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B.prototype.b = function() { return this._b; };
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assert.strictEqual(B.super_, A);
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const b = new B('b');
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assert.strictEqual(b.a(), 'a');
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assert.strictEqual(b.b(), 'b');
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assert.strictEqual(b.constructor, B);
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// two levels of inheritance
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function C() {
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B.call(this, 'b');
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this._c = 'c';
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}
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inherits(C, B);
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C.prototype.c = function() { return this._c; };
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C.prototype.getValue = function() { return this.a() + this.b() + this.c(); };
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assert.strictEqual(C.super_, B);
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const c = new C();
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assert.strictEqual(c.getValue(), 'abc');
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assert.strictEqual(c.constructor, C);
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// inherits can be called after setting prototype properties
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function D() {
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C.call(this);
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this._d = 'd';
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}
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D.prototype.d = function() { return this._d; };
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inherits(D, C);
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assert.strictEqual(D.super_, C);
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const d = new D();
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assert.strictEqual(d.c(), 'c');
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assert.strictEqual(d.d(), 'd');
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assert.strictEqual(d.constructor, D);
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// ES6 classes can inherit from a constructor function
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class E {
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constructor() {
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D.call(this);
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this._e = 'e';
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}
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e() { return this._e; }
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}
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inherits(E, D);
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assert.strictEqual(E.super_, D);
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const e = new E();
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assert.strictEqual(e.getValue(), 'abc');
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assert.strictEqual(e.d(), 'd');
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assert.strictEqual(e.e(), 'e');
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assert.strictEqual(e.constructor, E);
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// should throw with invalid arguments
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assert.throws(function() {
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inherits(A, {});
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}, common.expectsError({
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code: 'ERR_INVALID_ARG_TYPE',
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type: TypeError,
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message: 'The "superCtor.prototype" property must be of type function'
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})
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);
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assert.throws(function() {
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inherits(A, null);
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}, errCheck);
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assert.throws(function() {
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inherits(null, A);
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}, common.expectsError({
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code: 'ERR_INVALID_ARG_TYPE',
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type: TypeError,
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message: 'The "ctor" argument must be of type function'
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})
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);
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