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var F = function(selector, context) {
    return this.getNodeList(selector, context);
};
F.prototype.getNodeList = function(selector, context) {
    context = context || document;
    this.element = context.querySelectorAll(selector);
    return this;
};
F.prototype.hide = function() {
    var i=0, length = this.element.length;
    for (; i<length; i+=1) {
        this.element[i].style.display = "none";
    }    
};

var $ = function(selector, context) {
    return new F(selector, context);
};

$("button").element[0].onclick = function() {
    $("img").hide();  
};