custom.js

if (!Element.prototype.getElementByTagName) {
  Element.prototype.getElementByTagName = function(selector) {
    return this.getElementsByTagName(selector).item(0);
  }
}
if (!HTMLDocument.prototype.getElementByTagName) {
  HTMLDocument.prototype.getElementByTagName = function(selector) {
    return this.getElementsByTagName(selector).item(0);
  }
}

if (!Element.prototype.getElementByClassName) {
  Element.prototype.getElementByClassName = function(selector) {
    return this.getElementsByClassName(selector).item(0);
  }
}
if (!HTMLDocument.prototype.getElementByClassName) {
  HTMLDocument.prototype.getElementByClassName = function(selector) {
    return this.getElementsByClassName(selector).item(0);
  }
}

if (!HTMLDocument.prototype.getElementByName) {
  HTMLDocument.prototype.getElementByName = function(selector) {
    return this.getElementsByName(selector).item(0);
  }
}

if (!Element.prototype.getElementByTagName) {
  Element.prototype.getElementByTagName = function(selector) {
    return this.getElementsByTagName(selector).item(0);
  }
}
if (!HTMLDocument.prototype.getElementByTagName) {
  HTMLDocument.prototype.getElementByTagName = function(selector) {
    return this.getElementsByTagName(selector).item(0);
  }
}