Batarang regularInterceptedExpression

Question

I've been messing with the Batarang plugin recently to analyze some performance. I notice that at the top of every log there is a section dedicated to something called regularInterceptedExpression. Can anybody explain what this means and what are some ways to improve the performance. I read somewhere that is could be from using the '=' property in directives. If anyone else has seen this, is there a solution?

Answer 1

If you dig into AngularJS code, you can see function regularInterceptedExpression(scope, locals, assign, inputs) defined inside functionaddInterceptor(parsedExpression, interceptorFn). The only place where function addInterceptor(parsedExpression, interceptorFn) is used is function $parse(exp, interceptorFn, expensiveChecks). This is where the String and other watches are converted to functions. You need to update the angular.js file to

1) enhance the $parse(exp, interceptorFn, expensiveChecks) function to keep the source of the parsing:

Find the end of the method and each switch case end update with setting the $$source to the first argument of addInterceptor function.

      parsedExpression.$$source = exp; // keep the source expression handy
      return addInterceptor(parsedExpression, interceptorFn);

    case 'function':
      exp.$$source = exp; // keep the source expression handy
      return addInterceptor(exp, interceptorFn);

    default:
      noop.$$source = exp; // keep the source expression handy
      return addInterceptor(noop, interceptorFn);

2) inside the regularInterceptedExpression function collect the statistics of calls to that function:

 var fn = regularWatch ? function regularInterceptedExpression(scope, locals, assign, inputs) {
    var value = useInputs && inputs ? inputs[0] : parsedExpression(scope, locals, assign, inputs);
    window.$$rieStats = window.$$rieStats || {};
    window.$$rieStats[parsedExpression.$$source] = (window.$$rieStats[parsedExpression.$$source] ? window.$$rieStats[parsedExpression.$$source] : 0) + 1;
    return interceptorFn(value, scope, locals);

3) run you application and inspect the statistics i.e. open the Development Tools and write $$rieStats into the JavaScript console. You should see the numbers of watchers being called by the regularInterceptedExpression function.

Object.keys($$rieStats).sort(function(a,b){return $$rieStats[a]-$$rieStats[b]}).reverse().forEach(function(item){ console.log(item, $$rieStats[item])})

HINT: you can also add the $$rieStats counting to the other branch function oneTimeInterceptedExpression to track to one time binding as well.