完整的 JavaScript 自省(introspection)

Question

初级 JavaScript 问题。我有点被 Python 的 dir 内置函数宠坏了。我想发现 node.js REPL 中任何对象的属性/方法。我已经看过this question ;在空数组 [] 的简单情况下，接受的答案失败(在 node 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，我不认为这是正确的自省(introspection)。那么，有人可以在这里填写空白吗:

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，或者只适用于“用户类型”？

Answer 1

您需要在浏览器兼容性方面走多远？所有现代浏览器都应该支持 Object.getOwnPropertyNames()。使用您的示例，Object.getOwnPropertyNames([]) 将返回 ["length"]。

更多信息在这里:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames

编辑: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，既然您正在寻找完整的属性和方法列表，包括继承的属性和方法，我借用了其他两个 SO 问题(链接如下)并提出来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，如果您使用调用 findProperties([])，它会返回 ["length", "join", "reverse", "sort", "push", "pop", "shift", "unshift", "splice", "concat", "slice", "lastIndexOf", "indexOf", "forEach", "map", "reduce", "reduceRight", "filter", "一些”、“每个”、“迭代器”、“构造函数”、“toSource”、“toString”、“toLocaleString”、“valueOf”、“watch”、“unwatch”、“hasOwnProperty”、“isPrototypeOf”、“propertyIsEnumerable” , "__defineGetter__", "__defineSetter__", "__lookupGetter__", "__lookupSetter__"]

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