Detect markup symbols inside textarea

Question

I have a textarea on the page. And decide validate this element. I insert simple text and in js I check the length this element. But when I delete all text I can save without any problem. I see in firebug and in textarea I find

<ul></ul><br/>

}

// js

 for(var i=0; length > i; i++){
        value = textElements[i].value;
        if(value == "" ||(value == "<br/>" && element.tagName == "TEXTAREA")){
            full = false;
            emptyElements.push(elements[i]);
        } else {
            empty = false;
            elements[i].style.borderColor = "";
            elements[i].style.border = "";
        }
    }

Ad HTML

 <br /><div id="edit-contentFrame-form:editor" style="visibility:hidden"><textarea id="edit-contentFrame-form:editor_input" name="edit-contentFrame-form:editor_input"><h3></h3><h3></h3><h3><br/></h3><ul>
</ul></textarea></div>

I try to find existing way to resolve this problem. But nothing to find.

///EDITED

function isEmptyTextArea(){
                var str = document.getElementById('edit-contentFrame-form:editor_input').value;
                var regexp = new RegExp("(<+[\w]+>+)*", "g");
                var matches_array_tags = str.replace(regexp, '');

                if(matches_array_tags.length == 0){
                    return true;
                }
                return false;
            }

Answer 1

如果您不希望人们能够输入html，则可以使用正则表达式来替换文本区域中的所有“标记符号”标签，并将其剥离。

Answer 2

var txtarea = document.getElementById('txtarea');
if(escape(txtarea.value) === '')
     // textarea is empty

Not including whitespaces:

if(escape(txtarea.value.trim()) === '')
     // textarea is empty (not including whitespaces)

Answer 3

I resolve my problem with next js function

function isCompleteTagContent(str){
    var re= /<\S[^><]*>/g;
    var matches_array_tags = str.replace(re, "");

    if(matches_array_tags.trim().length == 0){
        return true;
    }
    return false;
}