Variable scope inside function Javascript

I am trying to validate form but whenever I click submit button it says:

ReferenceError: check_text is not defined

even though variable is present in local scope.

<form class="input-text-box" method="post" action="">
    <input type="text" id="uname" name="uname" placeholder="First Name" autocomplete="off" required>                        
    <input type="text" id="ulastname" name="ulastname" placeholder="Last Name" autocomplete="off" required>
    <input type="text" id="uuname" name="uuname" placeholder="Username" autocomplete="off" required>
    <input type="text" id="contact" name="contact" placeholder="Contact" autocomplete="off" required>
    <input type="email" id="email" name="uemail" placeholder="Email Address" autocomplete="off" required>
    <input type="password" id="pass-1" name="upass1" placeholder="Password" autocomplete="off" required>
    <input type="password" id="pass-2" name="upass2" placeholder="Confirm Password" autocomplete="off"required>
    <input type="submit" value="Sign Up" id="submit-btn" onclick="validate()">
     <p class="term-cond">By joining, you agree to our <a href="">Terms of Service</a> </p>
     <p class="term-cond" style="margin:40px 0 0 65px;">Already a member? <a href="login.html">Sign In</a> </p>
</form>

Below is the Javascript code which is intended to validate the values:

var msg="";
  var DOMstring = {
  firstName:'uname',
  lastName:'ulastname',
  userName:'uuname',
  contact:'contact',
  email:'email',
  pass1:'pass-1',
  pass2:'pass-2',
  submit:'submit-btn'
}
function validate(){
  var status = false;
  var firstName = document.getElementById(DOMstring.firstName).value;
  status = checkText(firstName,'First Name');
  var lastName = document.getElementById(DOMstring.lastName).value;
  status = checkText(lastName,'Last Name');
  var userName = document.getElementById(DOMstring.userName).value;
  status=checkText(userName,'Username');
  var contact = document.getElementById(DOMstring.contact).value;
  status = checkNumber(contact);
  var pass1 = document.getElementById(DOMstring.pass1).value;
  status = checkPass(pass1);
  var pass2 = document.getElementById(DOMstring.pass2).value;
  status = comparePass(pass1,pass2);

  if(status == true){
    alert("successfully created an account");
    return true;
  }else{
      alert("Please consider the following error messages<br>"+msg);
      return false;
   }
}

function checkText(DOMname,name){
  var ckeck_text =  /^[A-Za-z]$/;
  if(!check_text.test(DOMname)){
    msg += name + ' cannot contain numbers or special character.<br>';
    return false;
   }
 return true;
}

function checkNumber(DOMnumber){
  var check_number = /^[0-9]{10}$/;
  if(!check_number.test(DOMnumber)){
    msg += 'Number contains 10 digit only<br>';
    return false;
  }
  return true;
}

function checkPass(DOMpass1){
  var check_pass = /^(?=.*[\d])(?=.*[!@#$%^&*])[\w!@#$%^&*]{8,16}$/;
  if(!check_pass.test(DOMpass1)){
    msg += 'Password field should contain alphanumeric values and special character<br> and should be in range from 8 to 16<br>';
    return false;
  }
return true;
}

function comparePass(DOMpass1,DOMpass2){
  if(!DOMpass1 === DOMpass2){
    msg += 'Both password does not match<br>';
    return false;
  }
  return true;
}

I don't understand how there is no variable inside of same name if I had used let instead of var then this output is reasonable but with following method why it is not defined. If anything I am missing please help me to understand as I am completely new to Javascript.