else and else if

Learn else and else if chains for alternative cases.

else and else if

To run another block when the if condition is false you use else. In if (cond) { A } else { B } A runs when the condition is true; B when it is false.

To check several conditions in order you build an else if chain: if (a) { ... } else if (b) { ... } else { ... }. Dart checks top to bottom; it runs the first true block and skips the rest.

else if chain

To separate three or more cases you use else if. For example computing a grade: if (score >= 90) { print("A"); } else if (score >= 80) { print("B"); } else { print("C"); }.

Dart checks top to bottom; it runs the first true block and skips the rest of the chain. So putting the strictest condition first is efficient. The else block is optional; if no condition is true it is skipped.

Exercise Print the grade letter

Declare an int variable score with the value 75. If score >= 90 print print("A");, else if score >= 70 print print("B");, in the else block print print("C");. The output on a single line must be B.

Show example solution

int score = 75;
if (score >= 90) {
  print("A");
} else if (score >= 70) {
  print("B");
} else {
  print("C");
}

Test yourself

Write the else keyword

int score = 40;
if (score >= 50) {
  print("passed");
} ____ {
  print("failed");
}

Show answer

int score = 40;
if (score >= 50) {
  print("passed");
} else {
  print("failed");
}

When does the else block run?
```
if (cond) { A } else { B }
```
- when cond is always true
- when cond is true
- never
- when cond is false
Show answer

when cond is false — The else block runs when the if condition is false.
Match each part to its job

if (a)

First condition
else if (b)

Second condition
else

If none match
{ ... }

Block

Next lesson: switch

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