import_js_library.dart
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import 'dart:html' as html;
/// This is an implementation of the `import_js_library` plugin that is used
/// until that plugin is migrated to null safety.
/// See https://github.com/florent37/flutter_web_import_js_library/pull/6#issuecomment-735349208.
/// Imports a JS script file from the given [url] given the relative
/// [flutterPluginName].
void importJsLibrary({required String url, String? flutterPluginName}) {
if (flutterPluginName == null) {
_importJSLibraries([url]);
} else {
_importJSLibraries([_libraryUrl(url, flutterPluginName)]);
}
}
String _libraryUrl(String url, String pluginName) {
if (url.startsWith('./')) {
url = url.replaceFirst('./', '');
return './assets/packages/$pluginName/$url';
}
if (url.startsWith('assets/')) {
return './assets/packages/$pluginName/$url';
} else {
return url;
}
}
html.ScriptElement _createScriptTag(String library) {
final script = html.ScriptElement()
..type = 'text/javascript'
..charset = 'utf-8'
..async = true
..src = library;
return script;
}
/// Injects a bunch of libraries in the <head> and returns a
/// Future that resolves when all load.
Future<void> _importJSLibraries(List<String> libraries) {
final loading = <Future<void>>[];
final head = html.querySelector('head');
libraries.forEach((String library) {
if (!_isImported(library)) {
final scriptTag = _createScriptTag(library);
head!.children.add(scriptTag);
loading.add(scriptTag.onLoad.first);
}
});
return Future.wait(loading);
}
bool _isImported(String url) {
final head = html.querySelector('head')!;
return _isLoaded(head, url);
}
bool _isLoaded(html.Element head, String url) {
if (url.startsWith('./')) {
url = url.replaceFirst('./', '');
}
for (var element in head.children) {
if (element is html.ScriptElement) {
if (element.src.endsWith(url)) {
return true;
}
}
}
return false;
}