JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<meta charset="utf-8">
<body>
 
 
         <form id="myform">
          <input type="text" name="foo" />
        </form>
 
 
 <div id="myform3" class="general-formik standard-padding ">
   <form action="#">
      <div class="field field-comment">
         <div class="MuiFormControl-root MuiFormControl-fullWidth MuiTextField-root css-wb57ya-MuiFormControl-root-MuiTextField-root">
            <label class="MuiFormLabel-root MuiInputLabel-root MuiInputLabel-formControl MuiInputLabel-animated MuiInputLabel-shrink MuiInputLabel-outlined MuiFormLabel-colorPrimary Mui-error MuiFormLabel-filled MuiInputLabel-root MuiInputLabel-formControl MuiInputLabel-animated MuiInputLabel-shrink MuiInputLabel-outlined css-1sumxir-MuiFormLabel-root-MuiInputLabel-root" data-shrink="true" for="mui-59" id="mui-59-label">Describe your symptoms here</label>
            <div class="MuiInputBase-root MuiOutlinedInput-root MuiInputBase-colorPrimary Mui-error MuiInputBase-fullWidth MuiInputBase-formControl MuiInputBase-multiline css-8ewcdo-MuiInputBase-root-MuiOutlinedInput-root">
               <textarea rows="6" aria-invalid="true" autocomplete="off" name="describe_your_symptoms_here" placeholder="Text field" maxlength="700" class="MuiInputBase-input MuiOutlinedInput-input MuiInputBase-inputMultiline css-1sqnrkk-MuiInputBase-input-MuiOutlinedInput-input" id="mui-59" style="height: 138px;">xxx</textarea>
               <textarea aria-hidden="true" class="MuiInputBase-input MuiOutlinedInput-input MuiInputBase-inputMultiline css-1sqnrkk-MuiInputBase-input-MuiOutlinedInput-input" readonly="" tabindex="-1" style="visibility: hidden; position: absolute; overflow: hidden; height: 0px; top: 0px; left: 0px; transform: translateZ(0px); padding: 0px; width: 1115px;"></textarea>
               <fieldset aria-hidden="true" class="MuiOutlinedInput-notchedOutline css-1d3z3hw-MuiOutlinedInput-notchedOutline">
                  <legend class="css-14lo706"><span>Describe your symptoms...

JavaScript

document.getElementById("myform").elements["foo"]
document.getElementById("myform").elements["foo"].value = "Peter Pan"