htmlEncode.js

/*
HTMLEncode - Encode HTML special characters.
Copyright (c) 2006-2010 Thomas Peri, http://www.tumuski.com/
MIT License
*/

/*jslint white: true, onevar: true, undef: true, nomen: true, eqeqeq: true,
	plusplus: true, bitwise: true, regexp: true, newcap: true, immed: true */

/**
 * HTML-Encode the supplied input
 *
 * Parameters:
 *
 * (String)  source    The text to be encoded.
 *
 * (boolean) display   The output is intended for display.
 *
 *                     If true:
 *                     * Tabs will be expanded to the number of spaces
 *                       indicated by the 'tabs' argument.
 *                     * Line breaks will be converted to <br />.
 *
 *                     If false:
 *                     * Tabs and linebreaks get turned into &#____;
 *                       entities just like all other control characters.
 *
 * (integer) tabs      The number of spaces to expand tabs to.  (Ignored
 *                     when the 'display' parameter evaluates to false.)
 *
 * version 2010-11-08
 */
var htmlEncode = function (source, display, tabs) {
	var i, s, ch, peek, line, result,
		next, endline, push,
		spaces;

	// Stash the next character and advance the pointer
	next = function () {
		peek = source.charAt(i);
		i += 1;
	};

	// Start a new "line" of output, to be joined later by <br />
	endline = function () {
		line = line.join('');
		if (display) {
			// If a line starts or ends with a space, it evaporates in html
			// unless it's an nbsp.
			line = line.replace(/(^ )|( $)/g, '&nbsp;');
		}
		result.push(line);
		line = [];
	};

	// Push a character or its entity onto the current line
	push = function () {
		if (ch < ' ' || ch > '~') {
			line.push('&#' + ch.charCodeAt(0) + ';');
		} else {
			line.push(ch);
		}
	};

	// Use only integer part of tabs, and default to 4
	tabs = (tabs >= 0) ? Math.floor(tabs) : 4;

	result = [];
	line = [];

	i = 0;
	next();
	while (i <= source.length) { // less than or equal, because i is always one ahead
		ch = peek;
		next();

		// HTML special chars.
		switch (ch) {
		case '<':
			line.push('&lt;');
			break;
		case '>':
			line.push('&gt;');
			break;
		case '&':
			line.push('&amp;');
			break;
		case '"':
			line.push('&quot;');
			break;
		case "'":
			line.push('&#39;');
			break;
		default:
			// If the output is intended for display,
			// then end lines on newlines, and replace tabs with spaces.
			if (display) {
				switch (ch) {
				case '\r':
					// If this \r is the beginning of a \r\n, skip over the \n part.
					if (peek === '\n') {
						next();
					}
					endline();
					break;
				case '\n':
					endline();
					break;
				case '\t':
					// expand tabs
					spaces = tabs - (line.length % tabs);
					for (s = 0; s < spaces; s += 1) {
						line.push(' ');
					}
					break;
				default:
					// All other characters can be dealt with generically.
					push();
				}
			} else {
				// If the output is not for display,
				// then none of the characters need special treatment.
				push();
			}
		}
	}
	endline();

	// If you can't beat 'em, join 'em.
	result = result.join('<br />');

	if (display) {
		// Break up contiguous blocks of spaces with non-breaking spaces
		result = result.replace(/ {2}/g, ' &nbsp;');
	}

	// tada!
	return result;
};