Conditional Statements

Conditional statements choose which branch to execute based on an expression's truthiness.

const score = 82;

if (score >= 90) {
  console.log("Excellent");
} else if (score >= 70) {
  console.log("Good");
} else {
  console.log("Keep practising");
}

Conditions are checked from top to bottom. Put the most appropriate conditions in an order that prevents a broad condition from hiding a more specific one.

switch#

Use switch when comparing one expression against several discrete cases:

const role = "editor";

switch (role) {
  case "admin":
    console.log("Full access");
    break;
  case "editor":
    console.log("Can edit content");
    break;
  default:
    console.log("Read-only access");
}

The break statements prevent execution from falling through to the next case. Intentional fall-through should be documented. For many simple mappings, an object lookup can be easier to maintain than a long switch.

Avoid deeply nested logic#

Return early from functions when a condition means there is nothing more to do. This can reduce indentation and make validation steps easier to scan.

Practice#

Write a grading function that returns a label for a numeric score, and handle invalid scores explicitly.