Javascript check if exists and if not exists

Javascript check if exists and if not exists

by Adi Jaya

HTML

<div id="bar">
    <button onclick="cmd('bold');">B</button>
    <button onclick="cmd('italic');">I</button>
    <button onclick="cmd('underline');">U</button>
    <button onclick="viewsource();">Source</button>
</div>

<iframe id="editor"></iframe>
<textarea style="display:none;" id="textarea"></textarea>

CSS

*{
    box-sizing: border-box;
}
iframe,textarea {
    display : block;
    width : 100%;
    min-height:100px;
    border : 1px solid silver;
    margin : 10px 0;
    resize : vertical;
}

JavaScript

/*
if (selector) {
    //Do something if exists
}
if (!selector) {
    //Do something if not exists
}
*/

/*example*/
var target = document.getElementById('editor');

if (target) {
    var editor =  target.contentDocument||target.contentWindow.document;
    editor.designMode = 'on';
    editor.execCommand('defaultParagraphSeparator', false, 'p');
    
    var source = target.contentDocument.getElementsByTagName('body')[0];
    
    function cmd(key){
    	editor.execCommand(key);
    }
    
    function viewsource(){
    	var a = document.getElementById('textarea');
        a.style.display= "block";
        a.value= source.innerHTML;
    }
    //and more....
}

if (!target) {
    alert("Element [id=editor] not found");
    document.getElementById('bar').innerHTML="";
}