getElementsByClassName

Requirements

• Export getElementsByClassName as named and default. Accept a root Element and a whitespace-separated string of class names.
• Return a static array of matching descendants in document order; exclude the root itself. Every requested class must match a complete class token.
• Whitespace and duplicate requested class names are allowed. An empty or whitespace-only request returns [].
• Traverse the DOM yourself using children and classList. Do not use querySelector, querySelectorAll, or native getElementsByClassName.
• Do not mutate the DOM. The tests create the HTML fixture; no HTML or CSS files need to be written.

Examples

Input: getElementsByClassName(root, "card active");
Output: An array of descendant elements containing both card and active.