gistfile1.txt

export namespace Html {
    let charToEntityRegex: RegExp;
    let entityToCharRegex: RegExp;
    let charToEntity: Map = {};
    let entityToChar: Map = {
        '&': '&',
        '>': '>',
        '&lt;': '<',
        '&quot;': '"',
        '&#39;': '\''
    }

    addEntityToCharacterMappings(entityToChar);

    function addEntityToCharacterMappings(entityToChar: Map) {
        let charKeys: string[] = [];
        let entityKeys: string[] = [];

        for (let entity in entityToChar) {
            let char = entityToChar[entity];
            charToEntity[char] = entity;
            charKeys.push(char);
            entityKeys.push(entity);
        }

        charToEntityRegex = new RegExp(`(${charKeys.join('|')})`, 'g');
        entityToCharRegex = new RegExp(`(${entityKeys.join('|')}|&#[0-9]{1,5};)`, 'g');
    }

    export function encode(value: string){
        return (!value) ? null : String(value).replace(charToEntityRegex, (match, capture) => {
            return charToEntity[capture];
        });
    }

    export function decode(value: string) {
        return (!value) ? null : String(value).replace(entityToCharRegex, (match, capture) => {
            return (capture in entityToChar) ? entityToChar[capture] : String.fromCharCode(parseInt(capture.substr(2), 10));
        });
    }
}