Is an if with a continue a good pattern to prevent excessive nesting while iterating over properties in Javascript?

Question

I normally use this pattern to iterate over object properties:

for(var property in object) {
   if(object.hasOwnProperty(property)) {
      ...
   }
}

I don't like this excessive indentation and recently it was pointed out to me that I could get rid of it by doing this:

for(var property in object) {
   if(!object.hasOwnProperty(property)) {
      continue;
   }

   ...
}

I like this because it doesn't introduce the extra level of indentation. Is this pattern alright, or are there better ways?

Answer 1

I personally prefer:

for(var property in object) if(object.hasOwnProperty(property)) {
     ...
}

There is no extra level of indentation because for, if, etc. will take the next statement if you leave out the curly braces. Since we put all of our code inside the if hasOwnProperty block it makes any braces for the for statement unnecessary.

Essentially it's equivalent to:

for(var property in object) {
   if(object.hasOwnProperty(property)) {
     ...
   } else {
      continue;
   }
}

Answer 2

Syntacticly I'd prefer something like this

function own(obj) {
  var ownprops = {};
  for (var prop in obj) 
    if (obj.hasOwnProperty(prop)) ownprops[prop] = 1;

  return ownprops;
}

for (var property in own(object)) {
 //code
}

Looks nice, but it entails two loops over the same object, not pretty performance wise.

The other way to do it is functionaly

function foreach(obj, func, thisp) {
  for (var prop in obj)
    if (obj.hasOwnProperty(prop)) func.call(thisp, obj[prop], prop);
}

foreach(object, function(val, key) {
  //code
});

Only one loop, but a function is called for every iteration, which is not great performance wise but better than the last solution. Note that it also clobbers the value of this, but you can pass that value explicitly as the optional 3rd argument.

Just some alternatives. The way you are doing it, and the way explained by Daniel is just fine, and without performance compromises.

Also, I'd like to point out that you do not have to indent your code for every single curly brace...