code: function validateString(node, match) {
              const isTemplateElement = node.type === "TemplateElement";
              const escapedChar = match[0][1];
              let isUnnecessaryEscape = !VALID_STRING_ESCAPES.has(escapedChar);
              let isQuoteEscape;
  
              if (isTemplateElement) {
                  isQuoteEscape = escapedChar === "`";
  
                  if (escapedChar === "$") {
  
                      // Warn if `\$` is not followed by `{`
                      isUnnecessaryEscape = match.input[match.index + 2] !== "{";
                  } else if (escapedChar === "{") {
  
                      /*
                       * Warn if `\{` is not preceded by `$`. If preceded by `$`, escaping
                       * is necessary and the rule should not warn. If preceded by `/$`, the rule
                       * will warn for the `/$` instead, as it is the first unnecessarily escaped character.
                       */
                      isUnnecessaryEscape = match.input[match.index - 1] !== "$";
                  }
              } else {
                  isQuoteEscape = escapedChar === node.raw[0];
              }
  
              if (isUnnecessaryEscape && !isQuoteEscape) {
                  report(node, match.index + 1, match[0].slice(1));
              }
          }
docs: Checks if the escape character in given string slice is unnecessary.
  
  @private
  @param {ASTNode} node - node to validate.
  @param {string} match - string slice to validate.
  @returns {void}