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@mwunsch
Last active August 29, 2015 14:19
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A blah implementation of a Zipper for the DOM
/* I'm not thrilled with this, but it should be enough to demonstrate ... something ... */
function Breadcrumb(el) {
this.path = el.parentElement ? new Breadcrumb(el.parentElement) : null;
this.left = el.previousElementSibling;
this.right = el.nextElementSibling;
}
function Zipper(tree, path) {
this.tree = tree;
this.crumb = new Breadcrumb(tree);
}
function hierarchyPanic(msg) {
throw new DOMError("HierarchyRequestError", msg);
}
Zipper.prototype.goLeft = function () {
if (!this.crumb.path) hierarchyPanic("cannot go left of top");
if (!this.crumb.left) hierarchyPanic("cannot go left of first");
return new Zipper(this.crumb.left);
}
Zipper.prototype.goRight = function () {
if (!this.crumb.path) hierarchyPanic("cannot go right of top");
if (!this.crumb.right) hierarchyPanic("cannot go left of last");
return new Zipper(this.crumb.right);
}
Zipper.prototype.goUp = function () {
if (!this.crumb.path) hierarchyPanic("cannot go up of top");
return new Zipper(this.tree.parentElement);
}
Zipper.prototype.goDown = function () {
var child = this.tree.firstElementChild
if (!child) hierarchyPanic("cannot go down from leaf");
return new Zipper(child);
}
Zipper.prototype.change = function (el) {
this.tree.parentElement.replaceChild(el, this.tree);
return new Zipper(el);
}
Zipper.prototype.insertRight = function (el) {
this.tree.parentElement.insertBefore(el, this.crumb.right);
return new Zipper(this.tree);
}
Zipper.prototype.insertLeft = function (el) {
this.tree.parentElement.insertBefore(el, this.tree);
return new Zipper(this.tree);
}
Zipper.prototype.insertDown = function (el) {
this.tree.appendChild(el);
return new Zipper(el);
}
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