Extracting the src attribute and content of  tags in HTML files in a directory
You can use getattr function to merge your two functions into a single one.

def extract_attribute(src, attr_name):
    for file in os.listdir(src):
        filepath = os.path.join(src, file)
    with open(filepath) as f:
        html = f.read()
    parser = HtmlParser(html)

    yield from getattr(parser, attr_name)


Note that in Python 3.3+ there is yield from statement so you can yield values directly from iterable without writing for loop

Now if you still want to have two separate functions instead of passing attribute_name argument each time you can use function partial from functools

from functools import partial

extract_src_js = partial(extract_attribute, attr_name='src')
extract_int_js = partial(extract_attribute, attr_name='script_text')


Please also note that I've removed dst parameter from your functions since it was not used, however if it's just a part of your function you wanted us to review, just return it back.