变量范围和更改节点中的全局变量

Question

I have an if-else block in the function. The result depends on the value of q. If the value of q is a "well-defined query"(ex:localhost:1235/docs/q?beaven) then it should print 4. If the query is not well defined ie. q={}(ex: localhost:1235/docs), the result should have code and message as their properties(with their respective values) and passed as JSON.

But, it is not happening. I am messing up with the scope. The Output is: ""

 function doSearch(app){

  return errorWrap(async function(req, res) {
    const q = req.query || {};
    try {
      // let results = await app.locals.finder.find(q);
      let results = "";
      // console.log(q);
      if(q === {}){
         results = {
          code: "BAD_PARAM",
          message: "required query parameter \"q\" is missing"
         };
         res.json(results);
      // results = await app.locals.finder.find(q);
      }else{
        results == 4;
        res.json(results);
      }

    }
    catch (err) {
      const mapped = mapError(err);
      res.status(mapped.status).json(mapped);
    }
  });

}

Answer 1

if (q === {}) will never be true because === tests to see if the two are the exact same object (not if they have the same properties) and that will never be the case here because q and {} are always different objects.

You probably need to test if specific properties are present on q or not. Or you can test if (Object.keys(q).length === 0) to see if q is an empty object. But, I think probably what is best for your code is to see if the specific properties you're looking for on q are present or not.