A program constantly makes decisions: “if this is the case, then do that”. Those are conditions.

Useful operators

  • Arithmetic: +, -, *, /.
  • Comparison: === (equal to), !== (not equal to), >, <.
  • Logical: && (and), || (or).

The if / else structure

let age = 18;
if (age >= 18) {
  console.log("Majeur");
} else {
  console.log("Mineur");
}

The condition in brackets is evaluated: if it is true, the first block runs, otherwise the else block does. Watch out: you compare with three equals signs (===), whereas a single one (=) assigns a value.

Key takeaway: if / else lets a program respond to different situations. Compare with ===, never with a single =.

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