JavaScript Language

JavaScript Coercion and Equality Code Traces

Six output traces drilling on `==` vs `===`, unary `+`, falsy values, and chained relational coercion. Sharpens the rules JS applies before comparing.

JavaScript Hoisting and TDZ Code Traces

Six traces covering `var` declaration hoisting, function-declaration hoisting, TDZ access of `let`/`const`, and IIFE shadowing. Sharpens the mental model of when a binding exists vs. when it has a value.

JavaScript Object Reference and Key Coercion Traces

Six traces covering object-key stringification, reference vs literal equality, `Object.create` prototype chains, and shallow-copy aliasing with arrays.

JavaScript `typeof`, NaN, and Number Quirks Traces

Six traces covering the `typeof` chain, `isNaN` vs `Number.isNaN`, `parseInt` with `map`, the comma operator, `Object.is`, and `Number()` vs `new Number()`.

JavaScript Tooling and Build Trivia

Three quick-fire build-pipeline questions: transpiler vs polyfill, Babel vs SWC, and what source maps actually do.

JavaScript Cross-Browser Event Target: Two Approaches Quiz

Two seeded approaches to read the event target across browsers (event.target plus legacy event.srcElement, and a delegated table cell editor), plus two companions on currentTarget and composedPath.

JavaScript String-Only Regex Match: Three Approaches Quiz

Validate that a string contains only letters and whitespace, three ways (`String.prototype.match` + literal, `RegExp.test`, including-special-chars via `\D`), plus companions on Unicode letters and inverting the rule.

JavaScript Function Declaration vs Expression Hoisting: Two Explanations Quiz

Trace mixed declaration / expression calls before either is defined: declaration fully hoisted vs expression-as-var only binding hoisted, plus TDZ for let/const and named function expressions.

JavaScript Class Static vs Instance: Two Explanations Quiz

Two seeded explanations of how a `Person` class with a static method, a getter, and an instance method behaves when called via `new`, plus two companions on getter syntax and static field inheritance.

JavaScript Set and Map Values Output: Two Explanations Quiz

Two seeded explanations of how `Set` and `Map` expose their values via iterators and what `console.log` prints when you call `.values()` on each, plus two companions on insertion-order guarantees and on de-duplication semantics.