prettify-phone.pipe.ts

import { Pipe, PipeTransform } from '@angular/core';

interface ParsedPhone {
    code: string;
    mainPart: string;
}

@Pipe({
    name: 'prettifyPhone'
})

export class PrettifyPhonePipe implements PipeTransform {
    public transform(value: string, args: string[]): string {
        if (!value) { return value; }

        return this.prettify(value);
    }

    private parse(phone: string): ParsedPhone {
        let code = '';
        let mainPart = '';

        const normalizedPhone = phone.replace(/\s|-|\(|\)/g, '');
        const normalizedPhoneWithoutPrefix = normalizedPhone.replace(/^(\+7|8)/, '');
        const matchedCode = /\((\d+)\)/.exec(phone.replace(/\s|-/g, ''));

        if (matchedCode) {
            code = matchedCode[1];
        } else {
            if (
                normalizedPhoneWithoutPrefix.length === 10 &&
                (normalizedPhoneWithoutPrefix[0] === '9' || normalizedPhoneWithoutPrefix.indexOf('800') === 0)
            ) {
                code = normalizedPhoneWithoutPrefix.slice(0, 3);
            }
        }

        mainPart = normalizedPhoneWithoutPrefix.replace(code, '');

        return {
            code,
            mainPart
        };
    }

   private prettify(phone: string): string {
        const { code, mainPart } = this.parse(phone);

        let prefix = '';
        let formattedCode = '';
        let formattedNumber = '';

        if (code.length > 0) {
            // По умолчанию рассматриваем код, как код города
            formattedCode = `(${code}) `;

            if (code.length === 3) {
                // Если мобильний
                if (code[0] === '9') {
                    prefix = '+7 ';
                    formattedCode = `${code} `;
                }
                // Если 8-800-
                if (code === '800') {
                    prefix = '8 ';
                    formattedCode = `${code} `;
                }
            }
        }

        // Разбиваем основную часть номера на группы
        const matchedNumberGroups = mainPart.match(/(\d{0,3})(\d{2})(\d{2})/);

        formattedNumber = matchedNumberGroups
            ? `${matchedNumberGroups[1]}-${matchedNumberGroups[2]}-${matchedNumberGroups[3]}`
            : mainPart;

        return `${prefix}${formattedCode}${formattedNumber}`;
    }
}