Question

初学JavaScript问题。我有点被Python的dir内置函数所破坏。我想发现node.js REPL中任何对象的属性/方法。我已经看过this question;在一个空数组node的简单情况下，接受的答案失败（在[] REPL中）。例如：

for(var prop in []){console.log(prop);}  # returns undefined, prints nothing
[].length  # returns 0

由于for循环没有发现数组的length方法，所以我不认为这是正确的内省。那么，有人可以填补空白：

function magic(some_object) {
  # magic goes here
}

console.log(magic([]))  # should print a list that includes 'length'

或者这根本不可能，或者只能用于“用户类型”？

Answer 1

您需要多长时间才能获得浏览器兼容性？所有现代浏览器都应支持Object.getOwnPropertyNames()。使用您的示例，Object.getOwnPropertyNames([])将返回["length"]。

此处有更多信息：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames

修改：其他示例：

Object.getOwnPropertyNames([1, 2, 3]);返回["0", "1", "2", "length"]
Object.getOwnPropertyNames(String);返回["prototype", "quote", "substring", "toLowerCase", "toUpperCase", "charAt", "charCodeAt", "contains", "indexOf", "lastIndexOf", "startsWith", "endsWith", "trim", "trimLeft", "trimRight", "toLocaleLowerCase", "toLocaleUpperCase", "localeCompare", "match", "search", "replace", "split", "substr", "concat", "slice", "fromCharCode", "length", "name", "arguments", "caller"]

编辑＃2：好的，所以看到你正在寻找完整的属性和方法列表，包括继承的属性和方法，我借用了另外两个SO问题（链接如下）并且出现了一个似乎让你更接近的解决方案：

var findProperties = function(obj) {
    var aPropertiesAndMethods = [];

    do {
        aPropertiesAndMethods = aPropertiesAndMethods.concat(Object.getOwnPropertyNames(obj));
    } while (obj = Object.getPrototypeOf(obj));

    for ( var a = 0; a < aPropertiesAndMethods.length; ++a) {
        for ( var b = a + 1; b < aPropertiesAndMethods.length; ++b) {
            if (aPropertiesAndMethods[a] === aPropertiesAndMethods[b]) {
                aPropertiesAndMethods.splice(a--, 1);
            }
        }
    }

    return aPropertiesAndMethods;
}

因此，如果您使用致电findProperties([])，则会返回["length", "join", "reverse", "sort", "push", "pop", "shift", "unshift", "splice", "concat", "slice", "lastIndexOf", "indexOf", "forEach", "map", "reduce", "reduceRight", "filter", "some", "every", "iterator", "constructor", "toSource", "toString", "toLocaleString", "valueOf", "watch", "unwatch", "hasOwnProperty", "isPrototypeOf", "propertyIsEnumerable", "__defineGetter__", "__defineSetter__", "__lookupGetter__", "__lookupSetter__"]

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