Detect if function is native to browser

is_function_native_to_browser.js

var numf=0; var nump=0; var numo=0; 
for(var p in this) {
    if(typeof(this[p]) === "function"){
      if(this[p].toString().indexOf('[native code]') === -1){
        numf+=1;
        console.log(p+"()");
      }
    } else if(typeof p != 'undefined'){
        nump+=1;
        console.log(p);
    } else { 
        numo+=1;
        console.log(p);
    }
}