code: function concat(a,o,dest,p,replacement){
  
  	if(a.length > 0) {
  
  		var content = '';
  		// console.log(a);
  		// var a = a.reverse();
  		var rel = path.dirname(path.relative(dest,p));
  		fs.writeFileSync(o,'',{
  			encoding:'utf8'
  		});
  		a.forEach(function(v){
  			// var ap = path.resolve(pwd,dest,v);
  			var ap = path.resolve(pwd,dest,rel,v);
  			if(replacement){
  				ap = ap.replace(replacement.from,replacement.to);
  			}
  			if(!fs.existsSync(ap)){
  				return;
  			}
  			var str = read(ap).toString('utf8');
  			str += '\n';
  			fs.appendFileSync(o,str);
  		});
  		return read(o).toString('utf8');
  
  	} else {
  		return null;
  	}
  
  }
docs: ['a.js','b.js'] 'output.js' 'src/' 'src/~page/index.html' {from:/src/,to:'build'}