Interpolation module

@messagevisor/module-interpolation performs lightweight placeholder replacement such as {name}. It is useful when you want simple substitution without bringing in the full ICU syntax model.

Install#

Command

$ npm install @messagevisor/module-interpolation

Configure#

messagevisor.config.js

const { createInterpolationModule } = require("@messagevisor/module-interpolation");
module.exports = {
  modules: [createInterpolationModule()],
};

What it does well#

simple {name}-style replacement
lightweight authoring
compositions where ICU would be overkill

Custom placeholder patterns#

messagevisor.config.js

createInterpolationModule({
  pattern: /%\{([A-Za-z_][A-Za-z0-9_]*)\}/,
});

This can help if your project needs a placeholder syntax that avoids collisions with another templating system.

Compose with ICU#

Module ordering controls composition. Interpolation can run before ICU when you need both behaviors.

That means you should decide whether:

interpolation fills placeholders before ICU parsing
or ICU handles the string first

The right answer depends on how your authored messages are structured.

Edge cases and behavior notes#

This is runtime behavior#

Changing the interpolation module affects:

SDK output
CLI evaluation
examples
locale tests
target tests

Simpler does not always mean safer#

Interpolation is great for straightforward replacement, but if you need plural logic, ordinal behavior, or named format presets, ICU is usually the better fit.