Question

What is custom formatting?

Answer 1

You can use custom formatting for some of the formatting cases such as ICU formatting syntax (message "pattern" strings with variable-element placeholders enclosed in {curly braces}). It implement Formatter Interface.

// Custom Formatter implementation
class CustomFormatter {
     constructor (options) {
       // ...
     }
interpolate (message, values) {
       // return the interpolated array
       return ['resolved message string']
     }
}

// register with `formatter` option
const i18n = new VueI18n({
  locale: 'en-US',
  formatter: new CustomFormatter(/* here the constructor options */),
  messages: {
    'en-US': {
      // ...
    },
    // ...
  }
})

// Run!
new Vue({ i18n }).$mount('#app')