Control Flow

Theory

Control flow determines the order in which code executes. JavaScript provides conditionals for branching and loops for repetition.

Conditionals:

• if/else — the most common conditional. if (condition) { ... } else if (condition) { ... } else { ... }
• switch — evaluates an expression against multiple case labels. Use break to prevent fall-through
• Ternary operator condition ? exprIfTrue : exprIfFalse — a concise inline conditional for simple cases

Truthy and falsy values determine how conditions evaluate. Falsy values: false, 0, "" (empty string), null, undefined, NaN. Everything else is truthy, including "0", [], and {}.

Logical operators combine and manipulate conditions:

• && (AND) — returns the first falsy value or the last truthy value
• || (OR) — returns the first truthy value or the last falsy value
• ! (NOT) — negates a boolean value
• Nullish coalescing ?? — returns the right operand only if the left is null or undefined

Loops repeat code while a condition is true:

• for — classic loop with init, condition, and increment: for (let i = 0; i < n; i++)
• while — loops while a condition is true: while (condition) { ... }
• do...while — executes at least once, then checks condition
• for...of — iterates over iterable values (arrays, strings, Maps, Sets)
• forEach — array method that executes a function for each element

Break and continue: break exits a loop entirely. continue skips to the next iteration.

Exercises

for (let i = 1; i <= 15; i++) {\n  // Your code here\n}

1\n2\nFizz\n4\nBuzz\nFizz\n7\n8\nFizz\nBuzz\n11\nFizz\n13\n14\nFizzBuzz

Mini Quiz