Detailed introduction to href and onclick of a tag in html

I used to write the href and onclick of very casually. Later, several problems occurred, and then I started to pay attention to this issue:

##First excerpt A document:

In Javascript, void is an operator, which specifies that an expression is to be evaluated but does not return a value.

void operator usage format is as follows:

1. javascript:void (expression) 
2. javascript:void expression

expression is a Javascript standard expression to be evaluated. The parentheses outside the expression are optional, but are a good practice to write. (Implementation version Navigator 3.0)

You can use the void operator to specify a hyperlink. The expression will be evaluated but nothing will be loaded into the current document.

The following code creates a hyperlink that will cause nothing to happen to the user later. When the user links, void(0) evaluates to 0, but has no effect on the Javascript.

<A HREF="javascript:void(0)">单此处什么也不会发生</A>

The following code creates a hyperlink that will submit the form when the user clicks.

<A HREF="javascript:void(document.form.submit())">

Submit form here

The following code executes the subgo() function,

<a href="javascript:void(0)" onclick="subgo()">点我</a>

Here, javascript:void(0) has no actual function. It is just a dead link, and the executed function is subgo().

点我与<a href="javascript:void(0)" onclick="subgo()">点我</a>区别。

In fact #contains a location information. The default anchor is #top, which is the top of the web page, and javascript:void(0) only represents a dead link without any information. Therefore, it is best to use void(0) when calling a script

href generally points to a URL address, you can also call javascript, such as href="javascript:xxx();", document It is recommended to write like this: xx, but this method sometimes causes strange problems in complex environments, so try not to Using javascript: protocol as the href attribute of A will not only cause the window.onbeforeunload event to be triggered unnecessarily, but will also cause the gif animated image to stop playing in IE.

We know that the onclick event of the link is executed first, followed by the action under the href attribute (page jump, or javascript pseudo-link). If you do not want to execute the action under the href attribute Action execution, onclick needs to return false, generally write onclick="xxx();return false;".

JS source code of TabPane, because onclick does not return FALSE , when TABPANE is closed in IFRMAE, it will cause href execution and page display problems. The solution is to copy the following code into the JSP using TAB.

TabPane.prototype.appendTitle = function(tabpage){
  var td = $create("td");
  var strHTML = "<table class="" + TAB_STYLE_TABLE  + "" border="0" cellspacing="0" cellpadding="0"><tr>";
  strHTML +="<td><p class=""+TAB_STYLE_LEFT+""></p></td>";
  strHTML +="<td nowarp class=""+TAB_STYLE_MID+"">";
  strHTML +="<p style="white-space:nowrap;page-break-before: always;page-break-after: always;">";
  strHTML += tabpage.getTitle();
  strHTML +="</p></td>";
  if(tabpage.showCloseButton){
   strHTML +="<td nowarp class=""+TAB_STYLE_MID+"">";
   strHTML +="<a class="close" href="#" onclick="$o(\"" + this.id + "\").getTab(\"" + tabpage.id + "\").close();
return false;
">";
   if(isIE){
    strHTML +="<p></p></a>";
   }else{
    strHTML +="<p class="close"></p></a>";
   }
   strHTML +="</td>";
  }
  if(tabpage.allowReload){
   strHTML +="<td nowarp class=""+TAB_STYLE_MID+"">";
   strHTML +="<a class="reload" href="#" onclick="$o(\"" + this.id + "\").getTab(\"" + tabpage.id + "\").reload();
return false;
">";
   if(isIE){
    strHTML +="<p></p></a>";
   }else{
    strHTML +="<p class="reload"></p></a>";
   }
   strHTML +="</td>";
  }
  strHTML +="<td><p class=""+TAB_STYLE_RIGHT+""></p></p>";
  strHTML +="</td></tr></table>";
  td.className = TAB_STYLE_NOMAL + this.styleSuffix;
  td.innerHTML = strHTML;
  tabpage.__titleTD = td;
  tabpage.setTitleTD();
  tabpage.initStatus();
  this.__titleTR.insertBefore(td,this._titleTD);
  tabpage.titleWidth = td.offsetWidth;
}

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