discourse/app/assets/javascripts/discourse-common/addon/lib/attribute-hook.js

// FROM: https://github.com/Matt-Esch/virtual-dom
// License: MIT

function AttributeHook(namespace, value) {
  if (!(this instanceof AttributeHook)) {
    return new AttributeHook(namespace, value);
  }

  this.namespace = namespace;
  this.value = value;
}

AttributeHook.prototype.hook = function (node, prop, prev) {
  if (
    prev &&
    prev.type === "AttributeHook" &&
    prev.value === this.value &&
    prev.namespace === this.namespace
  ) {
    return;
  }

  node.setAttributeNS(this.namespace, prop, this.value);
};

AttributeHook.prototype.unhook = function (node, prop, next) {
  if (
    next &&
    next.type === "AttributeHook" &&
    next.namespace === this.namespace
  ) {
    return;
  }

  let colonPosition = prop.indexOf(":");
  let localName = colonPosition > -1 ? prop.substr(colonPosition + 1) : prop;
  node.removeAttributeNS(this.namespace, localName);
};

AttributeHook.prototype.type = "AttributeHook";

export default AttributeHook;