function A () { this.foo = function () {} } A.prototype.bar = function () {} function B(){} B.prototype = new A(); var a = new A(); var b = new B() console.log(b.__proto__===B.prototype) // true console.log(b.foo===a.foo) // false console.log(b.bar===a.bar) // true console.log(B.prototype===A.prototype) // false
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