TranslateParser API

The TranslateParser is responsible for interpolating translated messages with the parameters you pass in. You usually do not call it directly; it runs in the background each time a translation is requested.

The matching provider helper is provideTranslateParser(). See Configuration → Provider helpers.

API

export abstract class TranslateParser {
  abstract interpolate(
    expr: InterpolateFunction | string,
    params?: InterpolationParameters,
  ): string | undefined;
}

API Description

The interpolate() method takes either a string or a function expression and optional parameters, and returns the interpolated string.

Default parser behavior

With string expressions:

parser.interpolate('This is a {{key}}!', { key: 'banana' });
// 'This is a banana!'

With function expressions:

parser.interpolate((params) => `This is a ${params.key}`, { key: 'banana' });
// 'This is a banana!'

If you are not using a compiler, expr is always a string.

The parser is invoked on every translation lookup, so keep it lightweight. If parsing logic is expensive, move it into a compiler that runs once at load time.

Registering a Custom Parser

app.config.ts

import { provideTranslateService, provideTranslateParser } from '@ngx-translate/core';

export const appConfig: ApplicationConfig = {
  providers: [
    provideTranslateService({
      parser: provideTranslateParser(MyParser),
    }),
  ],
};

Factory form (e.g. when the parser needs configuration from inject()):

provideTranslateService({
  parser: provideTranslateParser(() => new MyParser({ strict: true })),
})

How to Build a Custom Parser

For a complete example see Write Your Own Parser.