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CSharp · Console

/Program.cs

using System;
using System.Text;
using System.Text.RegularExpressions;
					
public class Program
{
	private static string GetJsFile(string filename) {
		return @"function test1() {
		  return 'OK';
		}
		
		function test2(x) {
		  if (x == 2) {
		    return 'OK';
		  }
		}
		
		function test3(x,y) {
		  var x = '}`\'}';
		  var r = /}/;
		  // }
		  /* } 
		    }
		  */
		}
		
		function test4() {
		}";
	}
	
	private static string GetFunction(string jstext, string functionname) {

		var start = Regex.Match(jstext, @"function\s+" + functionname + @"\s*\([^)]*\)\s*{");
		
		if(!start.Success) {
   			throw new Exception("Function not found: " + functionname);		
		}
		
		StringBuilder sb = new StringBuilder(start.Value);
		jstext = jstext.Substring(start.Index + start.Value.Length);
		var brackets = 1;
		var i = 0;
		
		var delimiters = "`/'\"";
		string currentDelimiter = null;
		
		var isEscape = false;
		var isComment = false;
		var isMultilineComment = false;
		
		while(brackets > 0 && i < jstext.Length) {
			var c = jstext[i].ToString();
			var wasEscape = isEscape;
			
			if(isComment || !isEscape)
			{
				if(c == @"\") {
					// Found escape symbol.
					isEscape = true;
				} else if(i > 0 && !isComment && (c == "*" || c == "/") && jstext[i-1] == '/') {
					// Found start of a comment block
					isComment = true;
					isMultilineComment = c == "*";
				} else if(c == "\n" && isComment && !isMultilineComment) {
					// Found termination of singline line comment
					isComment = false;
				} else if(isMultilineComment && c == "/" && jstext[i-1] == '*') {
					// Found termination of multiline comment
					isComment = false;
					isMultilineComment = false;
				} else if(delimiters.Contains(c)) {
					// Found a string or regex delimiter
					currentDelimiter = (currentDelimiter == c) ? null : currentDelimiter ?? c;
				}

				// The current symbol doesn't appear to be commented out, escaped or in a string
				// If it is a bracket, we should treat it as one
				if(currentDelimiter == null && !isComment) {
					if(c == "{") {
						brackets++;
					}
					if(c == "}") {
						brackets--;
					}
				}

			}
			
			sb.Append(c);
			i++;
			
			if(wasEscape) isEscape = false;
		}
		
				
		return sb.ToString();
	}
	
	public static void Main()
	{
		var fileContent = GetJsFile("somefile.js");
		for(var i = 1; i < 5; i++) {		
			Console.WriteLine(GetFunction(fileContent, "test" + i));
			Console.WriteLine("-----------------------------------");
		}
	}
}