title: Regular expression acting weird?
body: <p>if I have:</p>
  
  <pre><code>var invalidCharacters = /[-+e.]/i; 
  </code></pre>
  
  <p>and</p>
  
  <pre><code>if(invalidCharacters.test(document.getElementById("postCode").value)) {
    var error_cardNo ="Please only use numbers in your post code.";
    document.getElementById("formTital").innerHTML=error_cardNo; 
    console.log("Test for invalidCharacters was true in cardNo");
    return;
  }
  </code></pre>
  
  <p>I then enter any input with  a "+", and it gets a pass, despite</p>
  
  <pre><code>var invalidCharacters = /[-+e.]/i;
  </code></pre>
  
  <p>The test is true if the input has "-", "e" and "." , why not "+"?</p>
  
  <p>Why do I not get a true on the test if my input has a +, and how do I fix it so I do get a true? This scenario is the same for several validations throughout my code. Let me know if you need the full function! </p>
  
  <p>(have mercy I'm new) </p>