Use JavaScript to implement comment and like functions

By analyzing the logical relationship of the comment function, learn how to use JavaScript to implement various functions such as comments, replies, and likes. This article mainly introduces how to implement the JavaScript comment and like function. Friends who need it can refer to

By analyzing the logical relationship of the comment function, you can learn how to use Javascript to implement various functions such as comments, replies, and likes.

1. Learn how to handle date and time with Javascript.

2. Master the method of adding/deleting child nodes in Dom operations.

3. Use setTimeout to set the timer.

4. Use clearTimeout to clear the timer and use the event agent.

Rendering:

1) Implement the function of deleting shared content

Use the event proxy to delete the shared content by clicking the close button.

Delete events:

Use the event proxy function to add events on the parent element node to reduce the amount of code and system running load.

When event proxying, use events The srcElement attribute in the object gets the trigger element.

IE browser supports window.event.srcElement, and firefox supports window.event.target.

So, if you want to be compatible in firefox, you only need to change one code: change var el = e.srcElement to var el = e.srcElement || e.target

removeChild() refers to Delete the child element, so to delete the current element el, first use parentNode to find the parent node, and then use removeChild(el) to delete the el element.

var list = document.getElementById('list');
      var boxs = document.getElementsByClassName('box');
      //删除节点函数
      function removeNode(node){
        node.parentNode.removeChild(node);
      }
      //事件代理
      for(var i=0 ;i<boxs.length;i++){
        boxs[i].onclick = function(e){
          e = e||window.event;
          var el = e.srcElement || e.target;
          switch (el.className) {
            case &#39;close&#39;:removeNode(el.parentNode);break;
          }
        }
      }

2) Implement the like function of sharing

Constructing a like and share function requires two parameters. The first parameter (box) represents the outermost parent of the like. Container, the second parameter (el) refers to the triggered element, that is, the like button

getAttribute() to get the attributes, and use setAttribute() to set the attributes of the element.

js code:

//点赞分享
      function praiseBox(box,el){//box为所触发元素el的最外层父容器
        var praiseElement = box.getElementsByClassName('praise-total')[0];
        var oldTotal = parseInt(praiseElement.getAttribute('total'));
        var txt = el.innerHTML;
        var newTotal = 0;
        if(txt == '赞'){
          newTotal = oldTotal + 1;
          praiseElement.innerHTML = (newTotal == 1) ? '我觉得很赞' : '我和' + oldTotal +'个人觉得很赞';
          el.innerHTML = '取消赞';
        }else{
          newTotal = oldTotal - 1;
          praiseElement.innerHTML = (newTotal == 0) ? '' : newTotal + '个人觉得很赞';
          el.innerHTML = '赞';
        }
        praiseElement.setAttribute('total',newTotal);
        praiseElement.style.display = (newTotal == 0) ? 'none': 'block';
      }
      //事件代理
      for(var i=0 ;i<boxs.length;i++){
        boxs[i].onclick = function(e){
          e = e||window.event;
          var el = e.srcElement || e.target;
          switch (el.className) {
            case &#39;close&#39;:removeNode(el.parentNode);break;
            case &#39;praise&#39;:praiseBox(el.parentNode.parentNode.parentNode,el);
          }
        }
      }

3) Implement the comment function

First of all, you must implement the change of the comment input box, by listening to three events

1. Obtain When the focus is on: onfocus

2. When the focus is lost: onblur

3. When the mouse input pops up: onkeyup

//输入框
        var textarea = boxs[i].getElementsByTagName('textarea')[0];
        textarea.onfocus = function(){
          this.parentNode.className = 'text-box text-box-on';
          this.value = (this.value == '评论...') ? '':this.value;
        }
        textarea.onblur = function(){
          if(this.value == ''){
            this.parentNode.className = 'text-box';
            this.value = '评论...';
          }
        }

4) Implement the reply button and word count functions

Add the onkeyup keyboard pop-up event to the textarea and learn to use the method of obtaining the parent node and child node.

In order to provide a better user experience, the input box will not immediately become smaller when it loses focus, so add a timer function in onblur. Note that the timer must be cleared when the gray reply button is clicked

js code:

textarea.onblur = function(){
          var me = this;//因为有定时器所以先将this存放于变量中
          timer = setTimeout(function(){
            if(me.value == ''){
              me.parentNode.className = 'text-box';
              me.value = '评论...';
            }
          },500);
        }
        textarea.onkeyup = function(){
          var len = this.value.length;
          var p = this.parentNode;
          var btn = p.children[1];
          var word = p.children[2];
          if(len == 0 || len > 140){
            btn.className = 'btn btn-off';
          }else{
            btn.className = 'btn';
          }
          word.innerHTML = len + '/140';
        }

5) Implement the comment sharing function

When the reply button is clicked, the content of the input box is added to the reply list by creating a p and adding a reply list, pay attention to changing part of the new reply list and the date of the comment to be changed.

js code:

//发表评论
      function replayBox(box){
        var textarea = box.getElementsByTagName('textarea')[0];
        var list = box.getElementsByClassName('comment-list')[0];
        var p = document.createElement('p');
        p.className = 'comment-box clearfix';
        p.setAttribute('user','self');
        var html = &#39; <img src="images/my.jpg" class="myhead" alt="" />&#39;+
            &#39;<p class="comment-content">&#39;+
            &#39;<p class="comment-text"><span class="user">我：</span>&#39;+textarea.value+&#39;</p>&#39;+
            &#39;<p class="comment-time">&#39;+
            getTime()+
            &#39;<a href="javascript:;" rel="external nofollow" rel="external nofollow" class="comment-praise" total="0" my="0" style="">赞</a>&#39;+
            &#39;<a href="javascript:;" rel="external nofollow" rel="external nofollow" class="comment-operate">删除</a>&#39;+
            &#39;</p>&#39;+
            &#39;</p>&#39;;
        p.innerHTML = html;
        list.appendChild(p);
        textarea.value = &#39;&#39;;
        textarea.onblur();
        function getTime(){
          var t = new Date();
          var y = t.getFullYear();
          var m = t.getMonth() + 1;//月份是从0开始
          var d = t.getDay();
          var h = t.getHours();
          var mi = t.getMinutes();
          m = m>10 ? m: &#39;0&#39; + m;
          d = d>10 ? d: &#39;0&#39; + d;
          h = h>10 ? h: &#39;0&#39; + h;
          mi = mi>10 ?mi: &#39;0&#39; +mi;
          return y + &#39;-&#39; + m + &#39;-&#39; + d + &#39; &#39; + h + &#39;:&#39; + mi;
        }
      }

5) Implement the like reply function

There is a my attribute in the a tag of the like button, which indicates whether you have liked it. When my When the value is 0, total will increase by one when the like button is clicked. When my value is 1, total will decrease by one when the like button is clicked.

js code:

//点赞回复
      function praiseReplay(el){
        var oldTotal = parseInt(el.getAttribute('total'));
        var my = parseInt(el.getAttribute('my'));
        var newTotal = 0;
        if(my == 0){
          newTotal = oldTotal + 1;
          el.setAttribute('total',newTotal);
          el.setAttribute('my',1);
          el.innerHTML = newTotal + '取消赞';
        }else{
          newTotal = oldTotal - 1;
          el.setAttribute('total',newTotal);
          el.setAttribute('my',0);
          el.innerHTML = (newTotal == 0) ? '' : newTotal + '赞';
        }
        el.style.display = (newTotal == 0) ? '' : 'inline-block';
      }

6) Implement the deletion and reply function of the content in the reply list

Reply to other people’s comments and delete your own comments

js code:

 //操作回复
      function operateReply(el){
        var commentBox = el.parentNode.parentNode.parentNode;//评论的容器
        var box = commentBox.parentNode.parentNode.parentNode;//该条分享的容器
        var textarea = box.getElementsByTagName('textarea')[0];
        var user = commentBox.getElementsByClassName('user')[0];
        var txt = el.innerHTML;
        if(txt == '回复'){
          textarea.onfocus();
          textarea.value = '回复' + user.innerHTML;
          textarea.onkeyup();
        }
        else{
          removeNode(el.parentNode.parentNode.parentNode);
        }
      }

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