The c‎wrapPlaceholder directive is used to put a value that will be removed from the DOM without removing its key from the final DOM render.

In this example, using c‎wrapPlaceholder will remove the placeholder value but preserve other values of the class key, as well as the class key itself, in the final DOM.

{
  "attributes": { 
    "href": "c‎wrapProperty[prefixAside=../]c‎wrapGlobal[documentation.advanced concepts.c‎wrapIndex]/", 
    "class": "c‎wrapArray[{‎{return c‎wrapReference.globals.const.documentation['advanced concepts'].map((x) =>  x !== c‎wrapRoute.replace('documentation/','') ? 'c‎wrapOmit' : 'focus')}‎}]" 
  }
}