Populate people picker field with logged in user in SharePoint using JS

Please use below code to populate people picker in SharePoint online,

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script type="text/javascript">
ExecuteOrDelayUntilScriptLoaded(function () {
setTimeout(function () {
SetUserFieldValue('AuthorName'); }, 1000);
}, 'clientpeoplepicker.js');

//Set PeoplePicker Value
function SetUserFieldValue(fieldName) {
try{
var userAccountName = _spPageContextInfo.userLoginName;
//PeoplePicker Object
var peoplePicker = $("div[title='" + fieldName + "']");
//PeoplePicker ID
var peoplePickerTopId = peoplePicker.attr('id');
//People PickerEditor
var peoplePickerEditor = $("input[title='" + fieldName + "']");
//Set Value to Editor
peoplePickerEditor.val(userAccountName);
//Get Client PeoplePicker Dict
var peoplePickerObject = SPClientPeoplePicker.SPClientPeoplePickerDict[peoplePickerTopId];
//Unresolve User From Editor
peoplePickerObject.AddUnresolvedUserFromEditor(true);
}catch(e) {

}
}//End Set PeoplePicker Value
</script>

Ref: https://jasonscript.wordpress.com/2013/08/07/javascript-and-working-with-the-sharepoint-2013-people-picker/