payalabs / scalajs-react-bridge   0.8.5

MIT License GitHub

A simple way to make React components in the wild usable in scalajs-react apps. Write a case class for each component and start using it in a type-safe manner in scalajs-react apps.

Scala versions: 2.13 2.12 2.11
Scala.js versions: 1.x 0.6

scalajs-react bridge

A boilerplate-free way to make React components in the wild usable in scalajs-react apps. Write an object for each component, use one of the four provided macros, and start using it in a type-safe manner in scalajs-react apps.

For example, to create a component corresponding to react-tagsinput, define a class as follows:

object TagsInput extends ReactBridgeComponent {
  def apply(defaultValue: js.UndefOr[Seq[String]] = js.undefined,
            value: js.UndefOr[Seq[String]] = js.undefined,
            placeholder: js.UndefOr[String] = js.undefined,
            onChange: js.UndefOr[js.Array[String] => Callback] = js.undefined,
            validate: js.UndefOr[String => CallbackTo[Boolean]] = js.undefined,
            transform: js.UndefOr[String => CallbackTo[String]] = js.undefined): WithPropsNoChildren = autoNoChildren

Then use it in a scalajs-react app the same way as any other component.

  TagsInput(value = Seq("foo","bar"), onChange = printSequence _)

If you want to pass DOM attributes as well as React special attributes such as "key" as additional properties, you can easily do so as follows:

  TagsInput(value = Seq("foo","bar"), onChange = printSequence _)(className := "tags", key := "key-1")

Finally, while TagsInput doesn't allow children (as signified by the return type of the method), if it were to, you could pass children as follows:

  TagsInput(value = Seq("foo","bar"), onChange = printSequence _)(className := "tags", key := "key-1")(
    div(className := "some-div")(
      span(className: "some-span")("content")

Getting started

Add the following dependency to your scalajs-react project:

libraryDependencies += "com.payalabs" %%% "scalajs-react-bridge" % "0.8.4"

To use the latest snapshot version

  1. Add the Sonatype snapshots resolver to your SBT configuration:
resolvers += Resolver.sonatypeRepo("snapshots")
  1. Add the following dependency to your scalajs-react project:
libraryDependencies += "com.payalabs" %%% "scalajs-react-bridge" % "0.8.5-SNAPSHOT"

Defining components

The core logic of bridging the JS React component to scala-react is implemented using the ReactBridgeComponent class and four macros in it that you can use as an implementation of an apply method (stricly speaking, you could use any name for the method, but then the component usage won't look as natural). The macro you will use depends on if the component allows children and if the component accepts arbitrary DOM attributes (TagsMods).

Can have children Cannot have children
Can take DOM attrs auto autoNoChildren
Cannot take DOM attrs autoNoTagMods autoNoTagModsNoChildren

Each of the macros return type that signify what has been already processed (and thus cannot process it again).

  • auto: WithProps (properties have been consumed, thus can pass TagMods followed by children)
  • autoNoChildren: WithPropsNoChildren (properties have been consumed, thus can pass TagMods, but that cannot be followed by children)
  • autoNoTagMods: WithPropsAndTags (properties have been consumed as are TagMods, thus can be followed by children)
  • autoNoTagModsNoChildren: WithPropsAndTagsNoChildren (properties, tags, and children have been consumed)

The easy path

ReactBridgeComponent offers an easy way to bridge a component when an object extending it follows these conventions:

  1. The object name matches the function name exposed for the underlying component. For example, if the component object is declared as object MyComponent extends ReactBridgeComponent { ... }, the correspoding MyComponent is available in the global space.
  2. The object has any number of apply methods taking properties as arguments. Each apply method may be implemented as either autoConstruct or autoConstructNoChildren. The default property transformation assumes that each method parameter type maps to the underlying component's expected property type and the parameter name match the underlying components property name. For example, if the underlying component expects a string property with name foo, then the parameter type must be String and parameter name must be foo. The bridge automatically translates (through implicit converters) parameters with Seq type (or its subtypes) to js array and Map types with String key type to js literal. You may provide custom conversions for your own types by introducing an implicit value of the JsWriter type.

Overriding the default

If a component cannot follow the expected conventions, it can override them as following:

  • If the class name doesn't match the function name, it can override componentName supply a different name.
  • If the function isn't exposed in the global space, it can override componentNamespace to supply the path to the function. For example, if the component function is exposed as, you can override componentNamespace to return
  • You may override componentValue to use any js.Any you can reference. This works well with @JSImported objects.
  • If overriding componentName and/or componentNamespace isn't sufficient, you may override jsComponent to supply the component function.
  • If an apply method's parameters require transformation beyond what is implemented by the macros, don't use the macros as their implementation. Instead, supply your own implementation, which may still use the jsComponent after transforming the method parameters appropriately.

Imports from other JavaScript modules

To import modules from NPM dependency, take a look at the following example:

object ReactBootstrapButton extends ReactBridgeComponent {

  @JSImport("react-bootstrap/Button", JSImport.Default)
  object RawComponent extends js.Object

  override lazy val componentValue = RawComponent

  def apply(variant: js.UndefOr[String] = js.undefined): WithProps = auto

Special cases

Passing DOM attributes to component

Oftentimes, React components allow adding any DOM attributes in addition to properties specific to that component. By default, bridged components allow passing any DOM attributes (as TagMods). Behind the scene, these attributes are merged with specific propeties passed. If you don't want this behavior, you can use the appropriate varation of macro described in the table earlier.

Component without any special properties

Oftentimes, especially with components that simply enhance a regular DOM element such as <input> don't need any special properties beyond what can be passed as DOM attributes. To handle those cases, scalajs-react-bridge offers ReactBridgeComponentNoSpecialProps (which extends ReactBridgeComponent). You can extend this class without implementing anything else thus making it a one-liner.

object Button extends ReactBridgeComponentNoSpecialProps

which then may be passed any DOM attributes (as TagMod):

Button(onClick --> handleClick)("Simple Button")

Component without any special properties and without children

As a further special case, certain components may not take any children, either. Those components may extend ReactBridgeComponentNoSpecialPropsNoChildren without implemented anything else thus making it a one-liner.

object Input extends ReactBridgeComponentNoPropsNoChildren

which then may be used as

Input(value := currentValue, onChange ==> handleChange)

Example components

See them live