How Do I Get the Class of a JavaScript Object?

Getting the Class of a JavaScript Object

In Java, the getClass() method enables retrieval of the class associated with an object. JavaScript, however, lacks an exact equivalent, primarily due to its prototype-based nature.

Determining Object Type and Classes

To determine the type or class of a JavaScript object, various options exist:

• typeof: Returns the data type of the object (e.g., "function" for classes, "object" for objects).
• instanceof: Tests if an object is an instance of a particular class (e.g., foo instanceof Foo).
• obj.constructor: Provides the constructor function used to create the object (e.g., foo.constructor.name).
• func.prototype, proto.isPrototypeOf: Determines if a prototype object is the prototype of a specified object (e.g., Foo.prototype.isPrototypeOf(foo)).

Examples:

function Foo() {}
var foo = new Foo();

typeof Foo;             // == "function"
typeof foo;             // == "object"

foo instanceof Foo;     // == true
foo.constructor.name;   // == "Foo"

Foo.prototype.bar = function (x) {return x+x;};
foo.bar(21);            // == 42

Note: Uglify, a code minification tool, may alter non-global class names. To prevent this, use the --mangle false parameter during compilation in Gulp or Grunt.

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