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JavaScript5 min read

Data Types

Read this chapter, write the program on this page, then pass a short check to open the next one.

Primitives and objects at a glance.

Data Types

JS has primitives (number, string, boolean, null, undefined, bigint, symbol) and objects (including arrays and functions).

  • typeof null is a historical quirk ("object").
  • Numbers are IEEE floats — watch precision.
  • Strings are immutable sequences of UTF-16 code units.
console.log(typeof 42, typeof "hi", typeof true, typeof undefined);

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