Welcome, all we will see Advanced JavaScript in Hindi. Reference Type in JavaScript. A variable can hold one of two value types: primitive values or reference values. Primitive values are data that are stored on the stack. Primitive value is stored directly in the location that the variable accesses. Reference values are objects that are stored in the heap. Reference value stored in the variable location is a pointer to a location in memory where the object is stored. Primitive types include Undefined, Null, Boolean, Number, or String. The Basics: Objects are aggregations of properties. A property can reference an object or a primitive. Primitives are values, they have no properties. Updated: JavaScript has 6 primitive data types: String, Number, Boolean, Null, Undefined, Symbol (new in ES6). With the exception of null and undefined, all primitives values have object equivalents which wrap around the primitive values, e.g. a String object wraps around a string primitive. All primitives are immutable.