Traversal.js

/** * Return the nth ancestor of e, or null if there is no such ancestor * or if that ancestor is not an Element (a Document or DocumentFragment e.g.). * If n is 0 return e itself. If n is 1 (or * omitted) return the parent. If n is 2, return the grandparent, etc. */ function parent(e, n) { if (n === undefined) n = 1; while(n-- && e) e = e.parentNode; if (!e || e.nodeType !== 1) return null; return e; } /** * Return the nth sibling element of Element e. * If n is postive return the nth next sibling element. * If n is negative, return the -nth previous sibling element. * If n is zero, return e itself. */ function sibling(e,n) { while(e && n !== 0) { // If e is not defined we just return it if (n > 0) { // Find next element sibling if (e.nextElementSibling) e = e.nextElementSibling; else { for(e=e.nextSibling; e && e.nodeType !== 1; e=e.nextSibling) /* empty loop */ ; } n--; } else { // Find the previous element sibling if (e.previousElementSibing) e = e.previousElementSibling; else { for(e=e.previousSibling; e&&e.nodeType!==1; e=e.previousSibling) /* empty loop */ ; } n++; } } return e; } /** * Return the nth element child of e, or null if it doesn't have one. * Negative values of n count from the end. 0 means the first child, but * -1 means the last child, -2 means the second to last, and so on. */ function child(e, n) { if (e.children) { // If children array exists if (n < 0) n += e.children.length; // Convert negative n to array index if (n < 0) return null; // If still negative, no child return e.children[n]; // Return specified child } // If e does not have a children array, find the first child and count // forward or find the last child and count backwards from there. if (n >= 0) { // n is non-negative: count forward from the first child // Find the first child element of e if (e.firstElementChild) e = e.firstElementChild; else { for(e = e.firstChild; e && e.nodeType !== 1; e = e.nextSibling) /* empty */; } return sibling(e, n); // Return the nth sibling of the first child } else { // n is negative, so count backwards from the end if (e.lastElementChild) e = e.lastElementChild; else { for(e = e.lastChild; e && e.nodeType !== 1; e=e.previousSibling) /* empty */; } return sibling(e, n+1); // +1 to convert child -1 to sib 0 of last } }