a-or-an.pipe.ts

import { Pipe, PipeTransform } from "@angular/core";
import { isVowel } from "../utils/utils";
@Pipe({
    name: "a-or-an",
})
/**
 * Takes a string and returns the string prepended by 'a' or 'an'.
 * Uses both naive and holdout-list approaches.
 * @constructor
 * @param {string} stringEntity - Entity to prepend 'a' or 'an' to.
 */
export class AorAnPipe implements PipeTransform {
    private irregularMap: any = {
        aubergine: 'an',
        herb: 'an',
        honor: 'an',
        honorable: 'an',
        hour: 'an',
        mba: 'an',
        msc: 'an',
        'm.sc.': 'an',
        umbrella: 'an',
        unicorn: 'a',
    };
    transform(stringEntity: string): string {
        if (!stringEntity || stringEntity === "") {
            return "";
        }
        else {
            const firstWord = stringEntity.trim().split(" ")[0];
            if (this.irregularMap[firstWord.toLocaleLowerCase()]) {
                return `${this.irregularMap[firstWord.toLocaleLowerCase()]} ${stringEntity}`;
            } else {
                return (isVowel(stringEntity[0]))
                    ? `an ${stringEntity}`
                    : `a ${stringEntity}`;
            }
        }
    }
}