The string to escape. Null or undefined returns "".
The HTML-escaped string, safe for use in DOM text contexts.
Escapes &, <, > via a text node's HTML serialization — safe for HTML
TEXT / element-content contexts. It does NOT escape the quotes " and '; for an
attribute-value context use escapeAttribute, which escapes all five. (An earlier
version of this line claimed the quotes were escaped — they are not.)
Escape dangerous HTML characters to prevent XSS.