在javascript中查看对象（在引擎盖下） [英] Viewing objects in javascript ( under the hood )

问题描述

我非常好奇，如何对象在nodejs中显示，在这种情况下承诺。当使用 console.log（promiseObject）时，输出的类型为

Im very curious as to how objects are displayed in nodejs and in this case promises. When using console.log(promiseObject) the output is of type

{state： pending $

{state:pending}

自从函数 .then（）

尝试自己使用此代码

 function a(){

    var deferred = q.defer();

    setTimeout(function(){
        deferred.resolve();
    },4000)

    return deferred.promise;
}

var p1 = a()
console.log(p1) 
//outputs {state:pending} while i was expecting something like
//while i was expecting it to be {state:pending,then:function()}

对我来说感到非常神秘。我也有类似的问题在浏览器中打印对象，似乎有些字段是..隐藏？ （虽然我知道在javascript中没有这样的事情）

Feels very arcane to me. I've also had similar problems in printing objects in the browser, seems like some fields are.. hidden? ( though i know of no such thing in javascript )

推荐答案

使用调试器，你的浏览器可能是一个好的。 F12，然后点击下面的运行按钮，即可浏览Promise对象（适用于Chrome / Chromium，Edge和Firefox）：

Use a debugger, your browser has probably a good one. F12 in your browser and click the Run button below and you can explore a Promise object (works in Chrome/Chromium, Edge, Firefox):

console.clear();
var a = new Promise(function(res, rej) { res(); });
console.dir(a);

then（）， catch（）和其他函数位于 __ proto __ 属性中。

then(), catch() and other functions are in the __proto__ property.

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