TypeScript: Cannot find name of variable (set in conditional statement)

Question

I'm trying to assign the value of a variable based on a condition inside an if/else loop. However, it seems that TS cannot find the name of the variable because it's set in an if/else statement.

if (stageName === "prod") {
  let iStack = new ProdStack(app, `${BASE_NAME}-Infra-${stageName}`, iProps);
} else {
  let iStack = new InfraStack(app, `${BASE_NAME}-Infra-${stageName}`, iProps);
}
iDeploymentGroup.addStacks(iStack);

Cannot find name 'iStack'.

Is this not allowed in TS? Is there a workaround?

Answer 1

The let variable is block-scoped so declaring it within the if or else blocks doesn't expose it outside.

There are a few work-arounds you can use such as declaring the variable above the if..else but personally, I'd just go with a ternary

iDeploymentGroup.addStacks(
  stageName === "prod"
    ? new ProdStack(app, `${BASE_NAME}-Infra-${stageName}`, iProps)
    : new InfraStack(app, `${BASE_NAME}-Infra-${stageName}`, iProps),
);