Abstract class for creating localizable React components (TS & MobX)

Localizable.tsx

import * as React from 'react';
import { LocalizableStore } from './LocalizableStore';

export interface LocalizableProps {
    l10n : LocalizableStore;
}

export abstract class Localizable<PropsType extends LocalizableProps, StateType> extends React.Component<PropsType, StateType> {
    tl : (string : string) => string;
    __ : (strings : TemplateStringsArray, ...props : any[]) => string;
    fn : (fn : string, string : any) => string;

    constructor (props : PropsType) {
        super(props);

        this.tl = this.props.l10n.tl.bind(this.props.l10n);
        this.__ = this.props.l10n.__.bind(this.props.l10n);
        this.fn = this.props.l10n.fn.bind(this.props.l10n);
    }
}

LocalizableStore.tsx

import { observable } from 'mobx';

export interface LocalizableLanguage {
    strings : { [key : string] : string };
    fns     : { [key : string] : (...args : any[]) => string };
}

export interface LocalizableStrings {
    [key : string] : LocalizableLanguage;
}

export class LocalizableStore {
    @observable lang = 'en_US';

    private langs : LocalizableStrings;

    constructor (strings : LocalizableStrings) {
        this.langs = strings;

        this.tl = this.tl.bind(this);
        this.__ = this.__.bind(this);
        this.fn = this.fn.bind(this);
    }

    tl (string : string) : string {
        return this.langs[this.lang] && this.langs[this.lang].strings[string]
            || this.langs['en_US'] && this.langs['en_US'].strings[string]
            || string;
    }

    fn (fn : string, string : any) : string {
        return this.langs[this.lang] &&  this.langs[this.lang].fns[fn] && this.langs[this.lang].fns[fn](string)
            || this.langs['en_US'] &&  this.langs['en_US'].fns[fn] && this.langs['en_US'].fns[fn](string)
            || string;
    }

    __ (strings : TemplateStringsArray, ...props : any[]) : string {
        const buffer : string[] = [];

        strings.forEach((string, index) => {
            buffer.push(this.tl(string));

            if (props[index]) {
                buffer.push(this.tl(props[index].toString()));
            }
        });

        return buffer.join('');
    }
}