I have spent 10 or 20 minutes here and there probably a dozen times in the past year and never found a bulletproof answer to this question.
How do you check if a JavaScript object is an instance of Object, not a subclass?
One use case for this is to check if arguments[0] is an "options" hash vs. a "model" (MVC), both of which extend the native Object, but which should be treated differently.
I have tried these:
// some helper to get constructor name
function klassName(fn) {
if (fn.__name__) {
return fn.__name__;
}
if (fn.name) {
return fn.name;
}
return fn.toString().match(/\W*function\s+([\w\$]+)\(/));
};
var Model = function() {};
m = new Model;
o = {};
Object(o) === o; // true
Object(m) === m; // true, thought it might be false
klassName(o.constructor); // Object
klassName(m.constructor); // Model
That klassName(m.constructor) doesn't work in some cases (can't remember exactly, but maybe a regex.constructor, something like that). Maybe it does, don't know for sure.
Is there a bulletproof way to tell if something is an {} object?
I have spent 10 or 20 minutes here and there probably a dozen times in the past year and never found a bulletproof answer to this question.
How do you check if a JavaScript object is an instance of Object, not a subclass?
One use case for this is to check if arguments[0] is an "options" hash vs. a "model" (MVC), both of which extend the native Object, but which should be treated differently.
I have tried these:
// some helper to get constructor name
function klassName(fn) {
if (fn.__name__) {
return fn.__name__;
}
if (fn.name) {
return fn.name;
}
return fn.toString().match(/\W*function\s+([\w\$]+)\(/));
};
var Model = function() {};
m = new Model;
o = {};
Object(o) === o; // true
Object(m) === m; // true, thought it might be false
klassName(o.constructor); // Object
klassName(m.constructor); // Model
That klassName(m.constructor) doesn't work in some cases (can't remember exactly, but maybe a regex.constructor, something like that). Maybe it does, don't know for sure.
Is there a bulletproof way to tell if something is an {} object?
-
1
In JavaScript nothing is bulletproof. Not even the
Bulletprooffunction itself. :) – Kendall Frey Commented Apr 25, 2012 at 23:27 - 1 BTW - JavaScript does not have a subclass per-se. Only constructor functions and prototypes. – gnarf Commented Apr 25, 2012 at 23:58
3 Answers
Reset to default 12Might something as simple as
function isObj( test ) {
return test.constructor === Object;
}
Be what you are looking for?
Test in jsFiddle
You mean this? http://jsfiddle/elclanrs/ukEEw/
var o = {};
var re = /\d/;
var f = function(){};
var d = new Date();
var isObj = function(e){
return e.toString() === '[object Object]';
};
console.log( isObj(o) ); // True
console.log( isObj(re) ); // False
console.log( isObj(f) ); // False
console.log( isObj(d) ); // False
I would just change one thing
var isObj = function(e){
if(!e) return false; // change this line
return e.toString() === '[object Object]';
};