function checkInput(type) {
    var input = document.createElement("input");
    input.setAttribute("type", type);
    return input.type == type;
}

if (checkInput("date")) {
    alert("Supports date input"); 
}

检测 placeholder

function supports_input_placeholder() {
  var i = document.createElement('input');
  return 'placeholder' in i;
}

if (Modernizr.input.placeholder) {
  // your placeholder text should already be visible!
} else {
  // no placeholder support :(
  // fall back to a scripted solution
}

检测 video

普通的 tag 没有这个属性。

function supports_video() {
  return !!document.createElement('video').canPlayType;
}

more stuffs