纯原生操作input中type为checkbox

//大学经验最多选择三个，否则置灰 -----纯原生

        for(var i=0;i<document.querySelectorAll('.answer-box').length; i++){
            document.querySelectorAll('.answer-box')[i].addEventListener("click",function(){
                console.log(this.checked,this);
                if(this.checked){  //选中
                    console.log("选中");
                    this.parentElement.previousElementSibling.setAttribute("id","imggray"); //选中的添加id
                }else{  //取消选中
                    console.log("取消选中");
                    this.parentElement.previousElementSibling.removeAttribute("id");  //取消选中的删除id
                };
                
                var radios = document.querySelectorAll('input[type="checkbox"]:checked');
                // console.log(radios.length);
                if(radios.length === 3){ //选中三个时的逻辑
                    // console.log(radios.length,document.querySelectorAll(".chooseback img"));
                    for(var j=0;j<document.querySelectorAll(".chooseback img").length;j++){
                        //
                        if(!document.querySelectorAll(".chooseback img")[j].getAttribute("id")){ 
                            document.querySelectorAll(".chooseback img")[j].nextElementSibling.style.color = "gray";
                            document.querySelectorAll(".chooseback img")[j].nextElementSibling.firstElementChild.disabled = true;
                            document.querySelectorAll(".chooseback img")[j].setAttribute("class","imggray");
                        }
                    }
                }else{   //三个以下的逻辑
                    for(var j=0;j<document.querySelectorAll(".chooseback img").length;j++){
                        //全部恢复可点击状态
                        if(document.querySelectorAll(".chooseback img")[j].getAttribute("class") === "imggray"){
                            document.querySelectorAll(".chooseback img")[j].nextElementSibling.style.color = "#000";
                            document.querySelectorAll(".chooseback img")[j].nextElementSibling.firstElementChild.disabled = false;
                            document.querySelectorAll(".chooseback img")[j].removeAttribute("class","imggray");
                        }
                    }
                }
            })
        }

$('input:checkbox:checked')


$('input[type=checkbox]:checked')