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🔁 Control Structures

Nested Conditions

Project Evidence Required

Complex game logic (e.g. power-up + collision + direction).

Assessment Method

Code review: Multi-level conditionals

What it is

Nested conditions are if statements inside other if statements. They’re used when a check only makes sense after a previous check has passed — e.g. you can only ask ‘did the player land on top?’ if you’ve already confirmed ‘did the player collide at all?’.

Why it matters

Some logic genuinely can’t be flattened into a single compound expression. If condition B is only meaningful when condition A is true, nesting reflects that dependency clearly. A flat chain of && operators would conceal the structure.

How GateGame implements it

NPC interaction logic uses nested conditionals. The outer check verifies the iterated object is the right class (obj.class === Npc); the inner check confirms an interact method exists before calling it. This prevents undefined is not a function errors when an entity in the array doesn’t have an interact handler.

Code Example

// Nested: class check → method existence check → call
for (const obj of this.classes) {
  if (obj.class === Npc) {            // outer: is this an NPC?
    if (obj.data.interact) {          // inner: does it have interact()?
      if (player.isNear(obj)) {       // deeper: is player in range?
        obj.data.interact();
      }
    }
  }
}

Key Takeaway

Nest when each check depends on the previous one passing. Flatten when the conditions are independent.

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