In short
JavaScript's primitive types (string, number, boolean, null, undefined, symbol, bigint) plus the object type — knowing them cold prevents subtle bugs. Type coercion, equality rules, numeric edge cases, and object references are particularly important because JavaScript is dynamically typed.
How to learn this
- 1Use `typeof` on each primitive type in the console to see the results. Verify the behavior with realistic data and handle the failure or empty state as well.
- 2Learn the difference between `null` and `undefined` precisely. Focus on understanding the underlying reason it works, not only memorizing the definition.
- 3Understand that everything non-primitive (arrays, functions, objects) is an object.
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