javascript - unusual transitionend script behavior -

hey guys have @ script below ::

  function transitionend() {     var el = document.createelement('bootstrap')      var transendeventnames = {       webkittransition : 'webkittransitionend',       moztransition    : 'transitionend',       otransition      : 'otransitionend otransitionend',       transition       : 'transitionend'     }      (var name in transendeventnames) {         console.log(name);       if (el.style[name] !== undefined) {         return { end: transendeventnames[name] }       }     }     return false // explicit ie8 (  ._.)   }  transitionend(); 

now when script run following printed console :

"webkittransition"  "moztransition" 

now if remove if check inside for loop , run following script instead ::

  function transitionend() {     var el = document.createelement('bootstrap')      var transendeventnames = {       webkittransition : 'webkittransitionend',       moztransition    : 'transitionend',       otransition      : 'otransitionend otransitionend',       transition       : 'transitionend'     }      (var name in transendeventnames) {         console.log(name);     }     return false // explicit ie8 (  ._.)   }   transitionend(); 

what prints out following ::

"webkittransition"  "moztransition"  "otransition"  "transition" 

why , expecting above result printed in both scripts , why getting differennt results ?? , console.log(name); before if condition , why if condition affecting result ?

thank you.

alex-z .

it’s not if-statement, it’s return-statement cancels loop (and function).

function myfunction() {   console.log('hello');   return;    // unreachable code; never run   console.log('world'); } 

return statements in loops exact same thing.

function myfunction() {   for(var = 0; < 1024; i++) {     return i;   }    // unreachable code   console.log('hello world'); }