method

PluginBuilder.onLoad

onLoad(

constraints: PluginConstraints,

callback: OnLoadCallback

): this;

@param constraints

The constraints to apply the plugin to

@param callback

The callback to handle the import

@returns

this for method chaining

Bun.plugin({
  setup(builder) {
    builder.onLoad({ filter: /^hello:world$/ }, (args) => {
      return { exports: { foo: "bar" }, loader: "object" };
    });
  },
});

Referenced types

interface PluginConstraints

filter: RegExp
Only apply the plugin when the import specifier matches this regular expression
// Only apply the plugin when the import specifier matches the regex Bun.plugin({ setup(builder) { builder.onLoad({ filter: /node_modules/underscore/ }, (args) => { return { contents: "throw new Error('Please use lodash instead of underscore.')" }; }); } })
namespace?: string
Only apply the plugin when the import specifier has a namespace matching this string
Namespaces are prefixes in import specifiers. For example, "bun:ffi" has the namespace "bun".
The default namespace is "file" and it can be omitted from import specifiers.

type OnLoadCallback = (args: OnLoadArgs) => OnLoadResult | Promise<OnLoadResult>