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{"@context":"https://schema.org","@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What are the primitive data types in JavaScript?","acceptedAnswer":{"@type":"Answer","text":"JavaScript has 7 primitive data types: String, Number, Boolean, Null, Undefined, Symbol (ES6), and BigInt (ES2020). Primitives are immutable and compared by value."}},{"@type":"Question","name":"What is the difference between null and undefined in JavaScript?","acceptedAnswer":{"@type":"Answer","text":"undefined means a variable has been declared but not assigned a value. null is an intentional assignment indicating \"no value\". typeof undefined returns \"undefined\", while typeof null returns \"object\" (a historical bug)."}},{"@type":"Question","name":"How do I check the type of a variable in JavaScript?","acceptedAnswer":{"@type":"Answer","text":"Use the typeof operator to check primitive types (typeof x). For arrays, use Array.isArray(x). For null, check x === null. For objects and class instances, use instanceof."}},{"@type":"Question","name":"Is JavaScript dynamically typed?","acceptedAnswer":{"@type":"Answer","text":"Yes, JavaScript is dynamically typed, meaning variables can hold values of any type and can change types during runtime. You do not need to declare types when creating variables."}}]}