Detectar el tipo de una variable en Javascript

Código JavaScript:

var _getType = function( inp ) {
var type = typeof inp, match;
var key;
if (type == 'object' && !inp) {
return 'null';
}
if (type == "object") {
if (!inp.constructor) {
return 'object';
}
var cons = inp.constructor.toString();
if (match = cons.match(/(\w+)\(/)) {
cons = match[1].toLowerCase();
}
var types = ["boolean", "number", "string", "array"];
for (key in types) {
if (cons == types[key]) {
type = types[key];
break;
}
}
}
return type;
};

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