如果你只是想手动检查变量以帮助调试，只需启动调试器:

调试器;

直接进入浏览器控制台。

是也不是。几乎在任何情况下都说“不”。“是的”，但如果您想检查全局作用域，则只能以有限的方式进行。举个例子:

var a = 1, b = 2, c = 3;

for ( var i in window ) {
    console.log(i, typeof window[i], window[i]);
}

在150多个其他东西中，输出如下:

getInterface function getInterface()
i string i // <- there it is!
c number 3
b number 2
a number 1 // <- and another
_firebug object Object firebug=1.4.5 element=div#_firebugConsole
"Firebug command line does not support '$0'"
"Firebug command line does not support '$1'"
_FirebugCommandLine object Object
hasDuplicate boolean false

因此，可以在当前范围内列出一些变量，但它不可靠、不简洁、不高效或不容易访问。

一个更好的问题是，为什么要知道作用域内的变量是什么?

正如大家所注意到的:你不能。 但是你可以创建一个obj并将你声明的每个var赋值给那个obj。 这样你就可以很容易地检查你的vars:

var v = {}; //put everything here

var f = function(a, b){//do something
}; v.f = f; //make's easy to debug
var a = [1,2,3];
v.a = a;
var x = 'x';
v.x = x;  //so on...

console.log(v); //it's all there

你不能。

变量，函数声明的标识符和函数代码的参数，被绑定为变量对象的属性，这是不可访问的。

参见:

作用域链和标识符解析

你有多少时间?

如果你ḧ̸̬̦̒͑͝ͅa̵͍͖t̴̪̟̬̖̾̋͗̏ͅe̸̳̍͌͝你的cpu，你可以通过每一个有效的变量名，并评估每一个，看看它是否会产生一个值!

下面的代码段尝试了前1000个bruteforce字符串，这足以在作用域内找到虚构的变量名:

let alpha = 'abcdefghijklmnopqrstuvwxyz'; let everyPossibleString = function*() { yield ''; for (let prefix of everyPossibleString()) for (let char of alpha) yield `${prefix}${char}`; }; let allVarsInScope = (iterations=1000) => { let results = {}; let count = 0; for (let bruteforceString of everyPossibleString()) { if (!bruteforceString) continue; // Skip the first empty string try { results[bruteforceString] = eval(bruteforceString); } catch(err) {} if (count++ > iterations) break; } return results; }; let myScope = (() => { let dd = 'ddd'; let ee = 'eee'; let ff = 'fff'; ((gg, hh) => { // We can't call a separate function, since that function would be outside our // scope and wouldn't be able to see any variables - but we can define the // function in place (using `eval(allVarsInScope.toString())`), and then call // that defined-in-place function console.log(eval(allVarsInScope.toString())()); })('ggg', 'hhh'); })();

这个脚本将最终(经过很长时间)找到所有作用域变量名称，以及abc nifty和swell，我创建的一些示例变量。注意，它只会找到由字母组成的变量名。

let preElem = document.getElementsByClassName('display')[0]; let statusElem = document.getElementsByClassName('status')[0]; let alpha = 'abcdefghijklmnopqrstuvwxyz'; alpha += alpha.toUpperCase(); let everyPossibleString = function*() { yield ''; for (let prefix of everyPossibleString()) for (let char of alpha) yield `${prefix}${char}`; }; (async () => { let abc = 'This is the ABC variable :-|'; let neato = 'This is the NEATO variable :-)'; let swell = 'This is the SWELL variable :-D'; let results = {}; let batch = 25000; let waitMs = 25; let count = 0; let startStr = null; for (let bruteStr of everyPossibleString()) { try { if (bruteStr === '') continue; if (startStr === null) startStr = bruteStr; try { results[bruteStr] = eval(bruteStr); } catch(err) {} if (count++ >= batch) { statusElem.innerHTML = `Did batch of ${batch} from ${startStr} -> ${bruteStr}`; preElem.innerHTML = JSON.stringify(results, null, 2); count = 0; startStr = null; await new Promise(r => setTimeout(r, waitMs)); } } catch(err) { // It turns out some global variables are protected by stackoverflow's snippet // system (these include "top", "self", and "this"). If these values are touched // they result in a weird iframe error, captured in this `catch` statement. The // program can recover by replacing the most recent `result` value (this will be // the value which causes the error). let lastEntry = Object.entries(results).slice(-1)[0]; results[lastEntry[0]] = '<a protected value>'; } } console.log('Done...'); // Will literally never happen })(); html, body { position: fixed; left: 0; top: 0; right: 0; bottom: 0; margin: 0; padding: 0; overflow: hidden } .display { position: fixed; box-sizing: border-box; left: 0; top: 0; bottom: 30px; right: 0; overflow-y: scroll; white-space: pre; font-family: monospace; padding: 10px; box-shadow: inset 0 0 10px 1px rgba(0, 0, 0, 0.3); } .status { position: fixed; box-sizing: border-box; left: 0; bottom: 0px; right: 0; height: 30px; line-height: 30px; padding: 0 10px; background-color: rgba(0, 0, 0, 1); color: rgba(255, 255, 255, 1); font-family: monospace; } <div class="display"></div> <div class="status"></div>

我非常清楚，这在任何情况下都是不现实的

不。“作用域内”变量由“作用域链”决定，不能通过编程方式访问。

有关详细信息(相当多)，请查看ECMAScript (JavaScript)规范。这里有一个官方页面的链接，你可以在那里下载规范规范(PDF格式)，这里有一个官方的，可链接的HTML版本。

根据您对Camsoft的评论进行更新

The variables in scope for your event function are determined by where you define your event function, not how they call it. But, you may find useful information about what's available to your function via this and arguments by doing something along the lines of what KennyTM pointed out (for (var propName in ____)) since that will tell you what's available on various objects provided to you (this and arguments; if you're not sure what arguments they give you, you can find out via the arguments variable that's implicitly defined for every function).

所以除了你定义函数的作用域之外，你还可以通过其他方法找到其他可用的函数:

var n, arg, name;
alert("typeof this = " + typeof this);
for (name in this) {
    alert("this[" + name + "]=" + this[name]);
}
for (n = 0; n < arguments.length; ++n) {
    arg = arguments[n];
    alert("typeof arguments[" + n + "] = " + typeof arg);
    for (name in arg) {
        alert("arguments[" + n + "][" + name + "]=" + arg[name]);
    }
}

(你可以进一步了解更多有用的信息。)

不过，我可能会使用Chrome的开发工具(即使你通常不使用Chrome进行开发)或Firebug(即使你通常不使用Firefox进行开发)，或Opera上的Dragonfly，或IE上的“F12开发工具”之类的调试器。并通读它们提供的任何JavaScript文件。然后打他们的头找个合适的医生。: -)