jQuery jQuery.type() Method

What You’ll Learn

The jQuery.type() utility returns a lowercase string naming the kind of value you pass in — fixing typeof traps like null and arrays. This tutorial covers syntax, all return values, five worked examples, comparisons with typeof and Array.isArray(), and when to branch on type in jQuery plugins.

Introduction

JavaScript’s built-in typeof operator is quick but unreliable for several common values. typeof null returns "object". typeof [] also returns "object". Dates and regular expressions look like ordinary objects too.

jQuery provides jQuery.type() (also written $.type()) as a static utility that inspects values with the same internal logic jQuery uses throughout its own codebase. The result is a predictable lowercase string you can compare in if statements or plugin option validators.

Understanding the jQuery.type() Method

jQuery.type(obj) uses Object.prototype.toString under the hood and maps internal class tags to friendly names. It returns "null" for null, "array" for arrays, "date" for Date instances, and "regexp" for RegExp objects — cases where typeof misleads beginners.

The method accepts any JavaScript value: primitives, functions, DOM nodes, jQuery collections, and plain objects. Use it when you need one consistent type string across a jQuery project, especially before calling utilities like $.extend() or iterating with $.each().

📝 Syntax

General form of jQuery.type:

jQuery.type( obj )
// or
$.type( obj )

Parameters

• obj — any JavaScript value to inspect.

Return value

• A lowercase string: "undefined", "null", "boolean", "number", "string", "function", "array", "date", "regexp", or "object".

Minimal workflow

if ($.type(options) === "object") {
  settings = $.extend({}, defaults, options);
}

Examples Gallery

Each example uses $.type(). Open DevTools or use the Try-it links to run them interactively.

var checks = [
  [undefined, "undefined"],
  [null,      "null"],
  [true,      "boolean"],
  [3,         "number"],
  ["test",    "string"],
  [function () {}, "function"],
  [[],        "array"],
  [new Date(), "date"],
  [/test/,    "regexp"],
  [{},        "object"]
];

checks.forEach(function (pair) {
  console.log($.type(pair[0]) === pair[1]); // all true
});

true (×10 — every check passes)

console.log(typeof null);    // "object"  — misleading!
console.log($.type(null));   // "null"    — correct

if ($.type(value) === "null") {
  console.log("Value is explicitly null");
}

object
null
Value is explicitly null

var list = ["a", "b", "c"];
var map  = { 0: "a", 1: "b", length: 2 };

console.log(typeof list);       // "object"
console.log($.type(list));      // "array"
console.log($.type(map));       // "object" — array-like but not an array

object
array
object

var when = new Date();
var pattern = /^\d+$/;

console.log($.type(when));     // "date"
console.log($.type(pattern));  // "regexp"
console.log(typeof when);      // "object" — not specific enough

date
regexp
object

function initPlugin(target) {
  var t = $.type(target);

  if (t === "string") {
    return $(target);           // CSS selector
  }
  if (t === "function") {
    return target;              // ready callback
  }
  if (t === "object") {
    return $.extend({}, target); // settings object
  }
  return null;
}

console.log(initPlugin("#menu") instanceof jQuery); // true (if #menu exists)
console.log($.type(initPlugin({ speed: 300 })));   // "object"

true
object

🚀 Common Use Cases

• Plugin option validation — accept objects, strings, or functions and route each correctly.
• Null-safe merging — detect null before passing data to $.extend().
• Array vs object guards — iterate with $.each only after confirming the collection type.
• Date serialization — format Date instances differently from plain config objects.
• RegExp handling — skip re-compiling when input is already a regular expression.
• Legacy jQuery codebases — one consistent type string across IE-era projects.

📝 Notes

• Available since jQuery 1.4 — powers many internal jQuery type checks.
• Return values are always lowercase English strings.
• DOM elements and jQuery objects typically return "object" — use dedicated checks for those.
• Array-like objects (NodeList, arguments) are "object", not "array".
• NaN has type "number" — same as any other number per JavaScript rules.
• Related helpers: $.isArray(), $.isFunction(), $.isPlainObject(), $.isEmptyObject().

💡 Best Practices