html - Javascript add onclick unsuccessful -

my script :

function $(attr){     if(attr.charat(0) == "#"){         return document.getelementbyid(attr.substr(1));     }else{         if(attr.charat(0) == "."){             return document.getelementsbyclassname(attr.substr(1));         }else{             return document.getelementsbytagname(attr);         }     } }  object.prototype.onclick = function(script){     this.onclick = script; }  $("#hi").onclick(function(){alert("hi");}); 

in html it's label id hi.

when click button, nothing happened. should do?

extending object bad practice, wouldn't recommend it. in modern browsers want easy, can use queryselectorall, , add events addeventlistener:

// iife (immediately invoked function expression) var $ = (function() {   // constructor   function $(selector) {     // queryselectorall returns pseudo-array     this.el = toarray(document.queryselectorall(selector));   }   // elements array or element index   $.prototype.get = function(i) {     return == null ? this.el : this.el[i];   };   // public method add event   $.prototype.on = function(event, f) {     this.el.foreach(function(el) {       el.addeventlistener(event, f);     });     // chain     return this;   };   // shortcut click event   $.prototype.click = function(f) {     return this.on('click', f);   };   // coverts pseudo-arrays real arrays   function toarray(x) {     return array.prototype.slice.call(x);   }   // wrapper create instances   // without using "new" keyword   return function(x) {     return new $(x);   } }());  $('#hi').click(function(){alert('hi')}); 

fiddle