jquery.tk.codeedit.js

(function($){

	var insertAt = function(text, startPos, endPos, replacement) {
		return text.substring(0, startPos) + replacement + text.substring(endPos, text.length);
	};

	// http://stackoverflow.com/a/1738888/38729
	$.fn.codeEdit = function() {

		var $this = $(this);

		$this.each(function() {
			$this.keydown(function (e) {

				if (e.keyCode == 9) { // tab
					var insertedToken = "\t",
						startPos = this.selectionStart,
						endPos = this.selectionEnd,
						scrollTop = this.scrollTop;

					this.value = insertAt(this.value, startPos, endPos, insertedToken);
					this.focus();
					this.selectionStart = startPos + insertedToken.length;
					this.selectionEnd = startPos + insertedToken.length;
					this.scrollTop = scrollTop;

					e.preventDefault();
				} else if (e.keyCode == 13) { // enter
					var startPos = this.selectionStart,
						endPos = this.selectionEnd,
						text = this.value,
						textBeforeSelection = text.substr(0, startPos),
						linesBeforeStart = textBeforeSelection.split("\n"),
						lastLineBeforeStart = linesBeforeStart[linesBeforeStart.length - 1],
						tabsOnTheBeginningOfLine = lastLineBeforeStart.match(/^([\s]*)/);

					if (tabsOnTheBeginningOfLine.length) {
						var tabs = "\n" + tabsOnTheBeginningOfLine[0];

						this.value = insertAt(this.value, startPos, endPos, tabs);
						this.selectionStart = startPos + tabs.length;
						this.selectionEnd = startPos + tabs.length;
					}
					e.preventDefault();
				}
			});
		});

		return $this;
	}
}($));