JSFiddle - React, Tailwind, and code Playground
HTML
<div id="ctl00_cphMain_pnl_left">
<a href="#ctl00_cphMain_ctl03_Tree_Index_SkipLink"><img width="0" height="0" style="border-width:0px;" src="/WebResource.axd?d=vp_dPIRRqCpyFrxPBwqvPmsO-wa56CpxZGlT_T-AdX5QN0qJOs_wgfq4QMJwRILSj9XSONYmkJAe85CVEph0Q1SfUqs1&t=634604712479085897" alt="Skip Navigation Links."></a>
<div style="width:10px;font-size: 11px; font-family: Tahoma; font-weight: bold; text-align: left;" onclick="OnTreeClick(event)" id="ctl00_cphMain_ctl03_Tree_Index">
<table cellspacing="0" cellpadding="0" style="border-width:0;">
<tbody>
<tr>
<td><a href="javascript:__doPostBack('ctl00$cphMain$ctl03$Tree_Index','t1730b784-94ca-42d3-80aa-1c9c064e271c')"><img style="border-width:0;" alt="Collapse Clinics" src="/WebResource.axd?d=_533LbcrYzxclETTqT9E9lbjpoP9iiSVLn9WP908dD96sH9D2JXH4BN8Q2OdATM4TYJU67kfDSnJQpffp_ITMVu3Y839pir-IzEhB41mqu6U8EWb0&t=634604712479085897"></a>
</td>
<td style="white-space:nowrap;">
<input type="checkbox" id="ctl00_cphMain_ctl03_Tree_Indexn0CheckBox" name="ctl00_cphMain_ctl03_Tree_Indexn0CheckBox"><a id="ctl00_cphMain_ctl03_Tree_Indext0" href="javascript:__doPostBack('ctl00$cphMain$ctl03$Tree_Index','s1730b784-94ca-42d3-80aa-1c9c064e271c')" class="ctl00_cphMain_ctl03_Tree_Index_0">Clinics</a>
</td>
</tr>
</tbody>
</table>
<table cellspacing="0" cellpadding="0" style="border-width:0;">
<tbody>
<tr>
<td>
<div style="width:20px;height:1px"></div>
</td>
<td>
<img alt="" src="/WebResource.axd?d=Ptpr_s5NKQd2NhXQH_MiSClxDVR5ZHar9QZwFenhB3L_8-vIXRA_NHlxqP3iWPQWzSbDizVZ5YO8o3q4fX1XUhismQEMBdpf8AuHvaSyrvYco4WB0&t=634604712479085897">
</td>
<td style="white-space:nowrap;">
...
JavaScript
$(document).ready(function () {
$("div[id $= Tree_Index]").find("input[type=checkbox]:first").click(function () {
$(this).closest("div").find(':checkbox').attr('checked', this.checked);
});
});
$(document).ready(function(){
$("div[id $=Tree_Index]").find("input[type=checkbox]:first").click(function(
){
$(this).closet("div").find(':checkbox').attr('checked',this.checked);
});
});
}
)
})