title: What is the meaning of {0} in JavaScript
body: <p>In the code from <a href="https://stackoverflow.com/questions/1260984/jquery-validate-less-than/1261314#1261314">this answer</a>:</p>
  
  <pre><code>$.validator.addMethod('lessThanEqual', function(value, element, param) {
      return this.optional(element) || parseInt(value) &lt;= parseInt($(param).val());
  }, "The value {0} must be less than {1}");
  </code></pre>
  
  <p>What is the meaning of <code>{0}</code> and <code>{1}</code>? What is the rule of thumb in Javascript to define those parameter replacements?</p>
  
  <p>So based on the comments, I want to further ask in order to pass {0} and {1} here.</p>
  
  <p>What is the syntax I have to use for validation function lessThanEqual.</p>
  
  <p>thank you</p>