HTML IE Conditionals + Pug / Jade

ie.pug

mixin ie(method, version)
  -
    version = (typeof version === 'number') ? `IE ${version}` : 'IE';
    method = method || '==';

    var condition = '';

    switch (method) {
      case '==':
        condition = version;
        break;
      case '!=':
        condition = `!${version}`;
        break;
      case '>':
        condition = `gt ${version}`;
        break;
      case '>=':
        condition = `gte ${version}`;
        break;
      case '<':
        condition = `lt ${version}`;
        break;
      case '<=':
        condition = `lte ${version}`;
        break;
    }

  <!--[if #{condition}]>
  block
  <![endif]-->

index.pug

include ie

+ie('<=', 8)
  body.no-supported