recursively remove undefined from object (including parent)

Question

I'm trying to find a solution to a problem where I need to remove undefined from nested object including all parents if there are no values there, please consider example:

var test = {
  foo : {
    bar : {
      baz : undefined
    }
  },
  bar : 1
}

So my task is to remove baz along with bar and foo but still have bar at the root level; I know that it's trivial task to solve with 2 for loops, I'm just wondering if there are more elegant and clean solutions which will use recursive stack instead? Thanks in advance!

Answer 1

Depth-first recursion should be able to handle it:

function cleanse(obj, path) {
    Object.keys(obj).forEach(function(key) {
        // Get this value and its type
        var value = obj[key];
        var type = typeof value;
        if (type === "object") {
            // Recurse...
            cleanse(value);
            // ...and remove if now "empty" (NOTE: insert your definition of "empty" here)
            if (!Object.keys(value).length) {
                delete obj[key]
            }
        }
        else if (type === "undefined") {
            // Undefined, remove it
            delete obj[key];
        }
    });
}

Example:

var test = {
  foo : {
    bar : {
      baz : undefined
    }
  },
  bar : 1
};
cleanse(test);
function cleanse(obj, path) {
    Object.keys(obj).forEach(function(key) {
        // Get this value and its type
        var value = obj[key];
        var type = typeof value;
        if (type === "object") {
            // Recurse...
            cleanse(value);
            // ...and remove if now "empty" (NOTE: insert your definition of "empty" here)
            if (!Object.keys(value).length) {
                delete obj[key]
            }
        }
        else if (type === "undefined") {
            // Undefined, remove it
            delete obj[key];
        }
    });
}
console.log(test);

Note that that only visits own, enumerable properties of the objects whose names are not Symbols (ES2015+). If you also want to handle properties inherited from prototypes, or non-enumerable properties, or properties whose names are Symbols, you'll need to adjust to handle that. (You can get non-enumerable properties on an ES5 or later JavaScript engine via getOwnPropertyNames.)