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@jonbretman
Last active January 16, 2024 01:16
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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);
@L8D
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L8D commented Nov 6, 2013

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

@PhilJ
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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! ;)

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