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How can I check if a javascript variable is function type?
How i check if a variable is a function
for Array exist Array.isArray()
but Function.isFunction dos'nt exist
asked Oct 24, 2012 at 16:45
Rolando Corratge Nieves
1,2432 gold badges10 silver badges26 bronze badges
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stackoverflow.com/q/5999998Jonathan Lonowski– Jonathan Lonowski2012-10-24 16:47:57 +00:00Commented Oct 24, 2012 at 16:47
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1Worth mentioning that the accepted/best answer here is simpler than the referenced question, as this is just for node ( no compatibility issues )Adam Tolley– Adam Tolley2016-08-08 23:52:57 +00:00Commented Aug 8, 2016 at 23:52
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4 Answers
if (typeof variable === 'function') {
// do something
}
1 Comment
Frederik Krautwald
typeof class A {} === "function" is true.You can use the instanceof operator.
var fn = function() {};
var result = fn instanceof Function; // result will be true
It also respects prototypal inheritance.
Comments
Underscore.js is a library that has a lot of useful helpers, like the one you're looking for.
_ = require('underscore');
var aFunction = function() { };
var notFunction = 'Not a function';
_.isFunction(aFunction); // true
_.isFunction(notFunction); // false
1 Comment
tylucaskelley
I wouldn't use underscore for this case, given that the _.isFunction function is just
typeof obj == 'function' || false - github.com/jashkenas/underscore/blob/…var fn = function() {},
toString = Object.prototype.toString;
first way:
if( toString.call( function(){} ) === '[object Function]' ) {
//if is Function do something...
}
second way:
if( fn.constructor.name = 'Function' ) {
//if is Function do something...
}
Hope it helps cheers:)!
