function Dom(selector){
this.dom = document.querySelector(selector);
this.val = function (content) {
if(content){
this.dom.value = content
}else{
return this.dom.value;
}
}
}
function $(selector) {
return new Dom(selector);
}
$("input").val("value")

(function(window, undefined) {
jQuery = function(selector, context) {
return new jQuery.fn.init(selector, context);
}
jQuery.fn = jQuery.prototype = {
init: function(selector, context) {
this.dom = document.querySelector(selector)
},
val: function(content) {
if(content) {
this.dom.value = content
} else {
return this.dom.value;
}
}
}
jQuery.fn.init.prototype = jQuery.fn;
window.$ = jQuery;
})(window);
$("input").val("value")