javascript，原型无法制作自己的方法

Question

I need to get this working, but I dont know why dosent working? Any idea? Thanks for help!

(function( window ) {
    function select( selector ) {
        return document.querySelectorAll(selector);
    };

    select.prototype.attr = function(atitr)
    {
        return this.getAttribute(atitr);
    };

    window.j = select;
})( window );

console.log(j('.lol:last-child').attr('href'));

Answer 1

In the function you have:

function select( selector ) {
    return document.querySelectorAll(selector);
};

so select returns a NodeList, which doesn't inherit from select . Then there is:

window.j = select;

and

j(...).attr(...)

So select is called without new , so it doesn't create an instance of itself and assign it to this . Since that object isn't returned anyway, the returned object won't inherit from select even if you do call it with new .

Edit

You can return an object that has the DOM elements as a property, eg:

<div class="lol">
  <a href="d" class="lol">sadas11DA</a>
  <a href="d31" class="lol">sadas222DA</a>
</div>

<script>

(function(window) {
  function Select(selector) {
    this.nodes = document.querySelectorAll(selector);
  }

  Select.prototype.attr = function(attribute) {
  console.log(this.nodes);
    return this.nodes[0]? this.nodes[0].getAttribute(attribute) : null;
  }

  window.j = Select;
}(this))

console.log(new j('.lol:last-child').attr('href'));

</script>

Note the modified markup. Also passing of this rather than window since this can't be modified, window can.