Gotchas for JS/TS developers

Dart's syntax does have a few false friends for the JS/TS developers. Here are some of them to avoid confusion:

Semicolons

Semicolons are required in Dart. It may be a subject to change in the future however, here's the discussion.

const != const

Equivalent to JavaScript's const is a final.

const in Dart represents a compile-time declared value, not an unchangeable one.

Comparison operator ===

There are no === operator in Dart, == is the equivalent thanks to the Dart's type system.

Promise is Future

In Dart, an idea of a task that will be finished later and can be awaited for is called Future, unlike in JS/TS.

async keyword positioning

async keyword enabling await syntax in the function body is placed after the function name:

example() async {...}

Fat arrow functions

This code in Dart

example() => true;

means that the example() function will return true and can have only one operation performed. For multistep operations, use:

example() {

.. steps ..

return true;

}

It works for lambdas too, like so

onEventHappened = () { .. do stuff .. }

this in Dart is not as confusing as in JS so one way of defining lambdas is enough 😉

Method return types

Unlike in TS, return types are defined before function declaration:

bool example() {

return true;

}

Modules handling

No export keyword or module.exports object is present in Dart. Everything that is in the root level of the .dart file can be imported in other modules. To hide elements from other modules predicate the name of the element with _, effectively making it private for the module.

const importableByOtherModules = 100;

const _hiddenFromOtherModules = 101;

String templates

In Dart, you can use templates in both '' and "" strings like so

print('${method()}, $variable')

No backticks are required (or even supported).