建立build.yaml文件，并进行如下配置

targets:
  $default:
    builders:
      build_web_compilers|entrypoint:
        # These are globs for the entrypoints you want to compile.
        generate_for:
          - test/**.browser_test.dart
          - web/**.dart
        options:
          compiler: dart2js
          # List any dart2js specific args here, or omit it.
          dart2js_args:
            - -O0

在命令行执行如下命令

pub run build_runner build --output web:build -r

详细命令详解见如下命令工具
dart2js: Dart-to-JavaScript compiler
webdev 部署