else if Statement

An else if chain tests several conditions in order until one matches.

In this lesson, you will study the rule, run a complete TypeScript example, explain its output, and test a small change.

A chain supports multiple categories without executing all matching branches. Only the first satisfied branch runs; a final else can handle values that meet none of the earlier conditions. Order matters when ranges overlap.

Use the diagram to locate the checks, values or branches involved in the example.

Save this code as main.ts or paste it into the TypeScript Playground. The example uses fixed values so it runs without prompting for input.

TypeScript code

const score: number = 82;
 if (score >= 90) {
   console.log("A");
 } else if (score >= 75) {
   console.log("B");
 } else if (score >= 50) {
   console.log("C");
 } else {
   console.log("Needs improvement");
 }

Verified output

B

How to run locally: npx tsc --strict --target es2022 --module commonjs main.ts, then node main.js. When using a project configuration, run the matching project build instead.

82 does not meet >= 90 but meets >= 75. B prints and the remaining conditions are skipped.

Predict the output before you run the sample. Compare each line with the source expression that produced it, and distinguish the type checker’s work from what happens in JavaScript at runtime.

Do not put a weaker condition first, such as score >= 50 ahead of score >= 90, or high scores may be classified too early.

Debugging habit: when a change is rejected, read the exact compiler diagnostic and inspect the operand types. When it compiles but behaves unexpectedly, follow the values through the JavaScript expressions.

Test scores 90, 75, 49 and 100. Explain which comparison selects each result.

Challenge: write down your prediction first, run the changed source, and explain any difference. Return to the verified version before continuing.

else if Statement: A chain supports multiple categories without executing all matching branches.

JavaScript stops evaluating the chain once a branch is selected.

Before continuing, be able to explain what is checked before execution and what actually changes at runtime in the example above.