Как на javascript обрезать ссылку?

    var profilePhoto; 
    var profilePhotoElement = document.getElementById('profile_photo_link'); 
    if (profilePhotoElement) { 
      profilePhoto = profilePhotoElement.src || profilePhotoElement.href; 
      if (profilePhoto) { 
        console.log("Value:"); 
        console.log(profilePhoto); 
        profilePhoto = profilePhoto.substr(15, profilePhoto.length);  
      } else { 
        console.log("Both src and href properties are not defined."); 
      } 
    } else { 
      console.log("Cannot find element with id='profile_photo_link'."); 
    } 
    console.log("Result:"); 
    console.log(profilePhoto);

<a href="https://vk.com/photo11792890_264692886" id="profile_photo_link">photo link</a>

var str = "https://vk.com/photo11792890_264692886"; 
var result = str.match( /https:\/\/vk.com\/(\w+)/i ); 
alert(result[1]);