window.onBeforeError( myJavaScriptFunction ) with safer.js

window_onbeforeerror_event.js

///////////////////////////////////////////////////////

var safer = require_saferjs();

///////////////////////////////////////////////////////

var myObject = getBuggyCode();

///////////////////////////////////////////////////////

console.clear();
console.log('////////// Example #1: safer.js /////////////');
console.info('expected output    : undefined 10 undefined "yourBar"');
console.info('expected exception : ');
console.info('actuals:');

    myObject = getBuggyCode();
    myObject.myMethod("code is safe by defaults"); 


console.log('////////// Example #2: safer.failsafe /////////////');
console.info('expected output    : ');
console.info('expected exception : ReferenceError: nonExistingObject is not defined');
console.info('actuals:');

    safer.failsafe = false;

    try {

      myObject = getBuggyCode();
      myObject.myMethod("code is safe by defaults, but is OFF for now"); 

    }
    catch(e){

      console.error(e);

    }
     
console.log('////////// Example #3: safer.onbeforeerror /////////////');
console.info('expected warning   : Variable nonExistingObjectmight cause uncaught ReferenceError in nonExistingObject[\'XXX\'] expression');
console.info('expected output    : undefined "code errors can be catched before they happen" undefined "yourBar"n');
console.info('expected exception : ');
console.info('actuals:');

    safer.failsafe = true;

    safer.onbeforeerror = function(variable, expression){
        console.warn('Variable '+variable+'might cause uncaught ReferenceError in '+expression+' expression');
    }

    myObject = getBuggyCode();
    myObject.myMethod("code errors can be catched before they happen"); 


console.log('/////////////////////////////////////////////////////////');

function getBuggyCode(){

    var myObject = { 

        myFoo     : 'yourBar',  
            
        myMethod  : safer( 
                     function x(myArgument){ 
                       console.log( 
                            ((myArgument.missingProberty)), 
                            ((myArgument)), 
                            ((nonExistingObject['XXX'])), 
                            ((this.myFoo)) 
                       ); 
                       return ((myArgument)) || 'somethingElse'; 
                     })
    };

    return myObject;
}

/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////

function require_saferjs(){


	function replace(unsafe, params, body){
		
		var matches = unsafe.match(/([\w\d_\$]+)([\[\.][\w\d_\$'"\[\]\.]+)?/i) || ['',''];		
		
		var name = matches[1];
		var path = matches[2] || '';
		
		var argument = params.indexOf(name);
		if(argument>=0) name = 'arguments['+argument+']';

		var literal = (name+path).replace(/\"/ig,'\\"');
		var predicter = /^[.\(\[]/.test(path[0]) 
		         ? 'typeof '+name+'=="undefined" && safer.beforeerror("'+name+'", "'+literal+'") && '+literal
		         : literal;
		var resolver = '( '+predicter+' || safer.eval("'+literal+'",this,arguments))';
		
		return body.replace(unsafe, resolver);
	}

	function generate(params, body){
		
		var matches = body.match(/\(\(([\w\d_\$\[\]'"\.]+)\)\)/ig) || [];
		
		for(var i=0;i<matches.length;i++){
			var unsafe = matches[i];
			body = replace(unsafe, params, body);
		}
		
		return new Function(body);
	}

	function safer(fn){
		var source = fn.toString().replace(/\n/g, '');
		var pattern = /function\s*\w*\s*\((.*)\)\s*{(.+)}\s*\;?\s*/i;
		var matches = source.match(pattern) || ['',''];
		var params = matches[1].replace(/\s+/ig,'').split(',');
		var body = matches[2];
		return generate(params, body);
	}


    safer.failsafe = true;

    safer.beforeerror = function(variable, expression){
      return safer.onbeforeerror && safer.onbeforeerror(variable, expression)
          || safer.failsafe ? !safer.failsafe : {};
    };

	safer.eval = function(source, context, arguments){
		try{
			return new Function("return "+source).apply(context, arguments);
		}catch(e){
			return;
		}
	}

	return safer;
}