Looping through an Object (Tree) Recursively

In JavaScript or jQuery, traversing an object and its descendants can be achieved using the for...in loop:

for (var key in foo) {
  if (key == "child") {
    // Do something with child
  }
  if (key == "bar") {
    // Do something with bar
  }
  if (key == "grand") {
    // Do something with grand
  }
}

Note that the for...in loop iterates over all enumerable properties, including those inherited from the object's prototype. To avoid acting on inherited properties, use hasOwnProperty:

for (var key in foo) {
  if (!foo.hasOwnProperty(key)) continue;
  if (key == "child") {
    // Do something with child
  }
}

Recursive Looping

To loop recursively, create a recursive function:

function eachRecursive(obj) {
  for (var key in obj) {
    if (typeof obj[key] === "object" && obj[key] !== null) {
      eachRecursive(obj[key]);
    } else {
      // Do something with primitive value
    }
  }
}

This function can handle both objects and arrays, traversing their nested structure recursively.