Create a gist now

Instantly share code, notes, and snippets.

@jonbretman /type.js
Last active Dec 27, 2015

What would you like to do?
Simple type checking in JavaScript.
(function (root) {
var type = function (o) {
// handle null in old IE
if (o === null) {
return 'null';
}
// handle DOM elements
if (o && (o.nodeType === 1 || o.nodeType === 9)) {
return 'element';
}
var s = Object.prototype.toString.call(o);
var type = s.match(/\[object (.*?)\]/)[1].toLowerCase();
// handle NaN and Infinity
if (type === 'number') {
if (isNaN(o)) {
return 'nan';
}
if (!isFinite(o)) {
return 'infinity';
}
}
return type;
};
var types = [
'Null',
'Undefined',
'Object',
'Array',
'String',
'Number',
'Boolean',
'Function',
'RegExp',
'Element',
'NaN',
'Infinite'
];
var generateMethod = function (t) {
type['is' + t] = function (o) {
return type(o) === t.toLowerCase();
};
};
for (var i = 0; i < types.length; i++) {
generateMethod(types[i]);
}
if (typeof exports === "object" && exports) {
exports = type;
}
else if (typeof define === "function" && define.amd) {
define(type);
}
else {
root.type = type;
}
})(this);
@Starefossen

Nicely done!

@L8D
L8D commented Nov 6, 2013

Checkout http://jsperf.com/type-cecking for some performance comparisons…

@PhilJ
PhilJ commented Nov 29, 2013

Jon, I listend to you awesome talk at JSConf.eu 2013 and have been using the type() method you proposed in your presentation in some of my hobby projects since then (most usually to assert parameter values).

I'd love to see this as an npm plugin, that i don't need to copy it in every project! ;)

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment