How to get child element by ID in JavaScript?

If jQuery is okay, you can use find(). It's basically equivalent to the way you are doing it right now.

$('#note').find('#textid');

You can also use jQuery selectors to basically achieve the same thing:

$('#note #textid');

Using these methods to get something that already has an ID is kind of strange, but I'm supplying these assuming it's not really how you plan on using it.

On a side note, you should know ID's should be unique in your webpage. If you plan on having multiple elements with the same "ID" consider using a specific class name.

Update 2020.03.10

It's a breeze to use native JS for this:

document.querySelector('#note #textid');

If you want to first find #note then #textid you have to check the first querySelector result. If it fails to match, chaining is no longer possible :(

var parent = document.querySelector('#note');var child = parent ? parent.querySelector('#textid') : null;

Here is a pure JavaScript solution (without jQuery)

var _Utils = function (){    this.findChildById = function (element, childID, isSearchInnerDescendant) // isSearchInnerDescendant <= true for search in inner childern     {        var retElement = null;        var lstChildren = isSearchInnerDescendant ? Utils.getAllDescendant(element) : element.childNodes;        for (var i = 0; i < lstChildren.length; i++)        {            if (lstChildren[i].id == childID)            {                retElement = lstChildren[i];                break;            }        }        return retElement;    }    this.getAllDescendant = function (element, lstChildrenNodes)    {        lstChildrenNodes = lstChildrenNodes ? lstChildrenNodes : [];        var lstChildren = element.childNodes;        for (var i = 0; i < lstChildren.length; i++)         {            if (lstChildren[i].nodeType == 1) // 1 is 'ELEMENT_NODE'            {                lstChildrenNodes.push(lstChildren[i]);                lstChildrenNodes = Utils.getAllDescendant(lstChildren[i], lstChildrenNodes);            }        }        return lstChildrenNodes;    }        }var Utils = new _Utils;

Example of use:

var myDiv = document.createElement("div");myDiv.innerHTML = "<table id='tableToolbar'>" +                        "<tr>" +                            "<td>" +                                "<div id='divIdToSearch'>" +                                "</div>" +                            "</td>" +                        "</tr>" +                    "</table>";var divToSearch = Utils.findChildById(myDiv, "divIdToSearch", true);

(Dwell in atom)<div id="note">   <textarea id="textid" class="textclass">Text</textarea></div><script type="text/javascript">   var note = document.getElementById('textid').value;   alert(note);</script>