Question

如果我尝试获取{ ,:(: "", ,:): "", ,:-(: "", ,:-): "", 0:): "", 0:-): "", 8-): "", :"): "", :$: "", :'(: "", :'): "", :'-(: "", :'-): "", :'-D: "", :'D: "", :(: "", :): "", :*: "", :,'(: "", :,'-(: "", :,(: "", :,): "", :,-(: "", :,-): "", :,-D: "", :,D: "", :-"): "", :-$: "", :-(: "", :-): "", :-*: "", :-/: "", :-@: "", :-D: "", :-o: "", :-O: "", :-P: "", :-S: "", :-Z: "", :-|: "", :/: "", :@: "", :D: "", :o: "", :O: "", :P: "", :s: "", :z: "", :|: "", ;(: "", ;): "", ;-(: "", ;-): "", ]:): "", ]:-): "", B-): "", o:): "", O:): "", O:-): "", o:-): "", X-): "", x-): "" }且文档中根本没有p标记，则变量仍然不为空，但仍有一些内容。如果我做var allPTags = document.getElementsByTagName("p");，它就不会发出警报;如何比较空值？

Answer 1

试试这个：

var allPTags = document.getElementsByTagName("p");
if(allPTags.length>0){
  alert("stackoverflow"); // your message if any P tag is present.
}

Answer 2

因为结果是一个空数组，所以你应该执行以下操作：

function showParentDiv() 
{
    //I need a svg onload event is fired after its parent div is shown.
    //End function
    $("#parent_div").show();
}

Answer 3

试试这个：

    var allPTags = document.getElementsByTagName("p");
    var allPTagsCount = allPTags.length;
    if(allPTags !== "") { 
       alert(something);
    }

什么是javascript中的对象html集合

3 个答案: