从节点v0.11开始，你可以使用标准的util函数:

var util = require('util');
util.isFunction('foo');

有几种方法，所以我将把它们都总结一下

Best way is: function foo(v) {if (v instanceof Function) {/* do something */} }; Most performant (no string comparison) and elegant solution - the instanceof operator has been supported in browsers for a very long time, so don't worry - it will work in IE 6. Next best way is: function foo(v) {if (typeof v === "function") {/* do something */} }; disadvantage of typeof is that it is susceptible to silent failure, bad, so if you have a typo (e.g. "finction") - in this case the if will just return false and you won't know you have an error until later in your code The next best way is: function isFunction(functionToCheck) { var getType = {}; return functionToCheck && getType.toString.call(functionToCheck) === '[object Function]'; } This has no advantage over solution #1 or #2 but is a lot less readable. An improved version of this is function isFunction(x) { return Object.prototype.toString.call(x) == '[object Function]'; } but still lot less semantic than solution #1

if (typeof v === 'function') {
    // do something
}

从节点v0.11开始，你可以使用标准的util函数:

var util = require('util');
util.isFunction('foo');

@grandecomplex:你的解决方案相当冗长。如果这样写会更清楚:

function isFunction(x) {
  return Object.prototype.toString.call(x) == '[object Function]';
}

当然，下划线的方式更有效率，但当效率不是问题时，最好的检查方法是在@Paul Rosania的下划线页面上写的。

受下划线的启发，最后的isFunction函数如下:

function isFunction(functionToCheck) {
 return functionToCheck && {}.toString.call(functionToCheck) === '[object Function]';
}

注意:此解决方案不适用于异步函数、生成器或代理函数。请参阅其他答案，以了解更多最新的解决方案。