I want to add multiple languages to my spfx web part.

Now I want to import some interfaces to my mystrings.d.ts declaration file. But when I do that it breaks the definition and I get a lot of errors like:

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My question is if it's possible to import interfaces to my declaration file for my strings so that i don't have to write these definitions on my own?

  • import some interfaces to my "mystrings.d.ts" what do you mean by this? It is confusing. Are you using this interface in other TSX/JSX file? Oct 14, 2019 at 16:13

2 Answers 2


Please check the below steps for adding multiple language in SPFX webparts:

  1. Within "loc" folder you will see a file named "mystrings.d.ts". At first add property here like below:
declare interface ITestWebPartStrings {
  WebpartTitle: string;
  1. There is a file for english language named "en-us.js". If you want to add another language you have to create another file. For example if you want to add Norwegian language then you have to create "nb-NO.js" file.
  2. After that add the property in "nb-NO.js" file for Norwegian language. And for english language add property within "en-us.js" file as like below:
define([], function() {
    return {
        "WebpartTitle": "YourTitle",
  1. Now you have to import in your file.
import * as strings from 'TestWebPartStrings';
  1. Now you can show "WebpartTitle" using "strings.WebpartTitle". This is the process to add multiple language.
let wpTitle = strings.WebpartTitle;

If the answer is helpful, please upvote and mark as accepted.

  • 1
    First, thaks a lot. I think i didn't described my problem exactly. I know how to add multiple languages to my project. The probblem is that i e.g. use the fabric ui calendar and want to set the calendar strings into my language files. therefore i added the "ICalendarStrings" into my mystrings.d.ts file. But therefore i have to import the interface. But then i get the errors from above. Oct 15, 2019 at 6:55
  • You are welcome. Now your problem is clear. Oct 15, 2019 at 7:20

If you want to localize your SharePoint Framework web-part to use it for different languages then you can create multiple javascript files for each languages which will have definitions for properties of your web-part.

Follow below official documentation by Microsoft for the same:

Localize SharePoint Framework client-side web parts.

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