Question

Build a table

Use document.createElement to create new element nodes, document.createTextNode to create text nodes, and the appendChild method to put nodes into other nodes.

You should loop over the key names once to fill in the top row and then again for each object in the array to construct the data rows.

Don’t forget to return the enclosing <table> element at the end of the function.

Elements by tag name

The solution is most easily expressed with a recursive function, similar to the talksAbout function defined earlier in this chapter.

You could call byTagname itself recursively, concatenating the resulting arrays to produce the output. For a more efficient approach, define an inner function that calls itself recursively and that has access to an array variable defined in the outer function to which it can add the matching elements it finds. Don’t forget to call the inner function once from the outer function.

The recursive function must check the node type. Here we are interested only in node type 1 ( document.ELEMENT_NODE ). For such nodes, we must loop over their children and, for each child, see whether the child matches the query while also doing a recursive call on it to inspect its own children.

This is a book about getting computers to do what you want them to do. Computers are about as common as screwdrivers today, but they contain a lot more hidden complexity and thus are harder to operate and understand. To many, they remain alien, slightly threatening things.