How to access a JSON key with .filter()

Question

How would I filter out the following Titles using .filter ? I'm expecting the output to be something like: {"Capuchin Monkey", "Capybara"} I'm working with JSON that looks like this:

{
  "d": {
    "results": [
      {
        "__metadata": {
          "id": "N/A",
          "type": "N/A"
        },
        "Courses": {
          "results": [
            {
              "__metadata": {
                "id": "N/A",
                "type": "N/A"
              },
              "Title": "Capuchin Monkey"
            },
            {
              "__metadata": {
                "id": "N/A",
                "type": "N/A"
              },
              "Title": "Capybara"
            },

JS snippet:

// Courses/Title is what I'm interested in
    axios.get([redacted] + "/getByTitle('Categories')/items?$select=Title,Description,Courses/Title,SortOrder&$expand=Courses&$orderby=Title&$top=1000",
                {
                    method: "GET",
                    credentials: "include",
                    mode: "no-cors",
                    headers: {
                        "Accept": "application/json; odata=verbose"
                    }
                }),
   // irrelevant code
        ]).then(axios.spread((cat, lib, admn) => {
            _categories = cat.data.d.results; // -------- //

            this.loadCategories();
        })).catch(error => {
            console.log(error);
        });

getCategories(){ 
        return _categories;
    }

loadCategories(){ 
        let categs = _categories,
            trainingCrs = _categories.d.results.filter(x => {
                return {
                    "crsTitle": x.Courses.results.Title // code smell
                }
            });

Answer 1

I think you need is map, not filter. Something like this:

 var json = { "results": [ { "__metadata": { "id": "N/A", "type": "N/A" }, "Courses": { "results": [ { "__metadata": { "id": "N/A", "type": "N/A" }, "Title": "Capuchin Monkey" }, { "__metadata": { "id": "N/A", "type": "N/A" }, "Title": "Capybara" }]}}]}; const reducedResult = json.results.reduce((act, val)=> act.concat(val)); const titles = reducedResult.Courses.results.map((value)=>value.Title); console.log(titles); 

Answer 2

To get a list of Titles such as {"Capuchin Monkey", "Capybara"} , you better use Array​.prototype​.map() rather than Array​.prototype​.filter() .

 var json = { "d": { "results": [ { "__metadata": { "id": "N/A", "type": "N/A" }, "Courses": { "results": [ { "__metadata": { "id": "N/A", "type" : "N/A" }, "Title": "Capuchin Monkey" }, { "__metadata": { "id": "N/A", "type": "N/A" }, "Title": "Capybara" } ] } } ] } } // Use of .map trainingCrs = json.d.results[0].Courses.results.map(x => x.Title); console.log("Training title list: ", trainingCrs); // Use of .filter trainingCrs = json.d.results[0].Courses.results.filter(x => x.Title === "Capybara"); console.log("Training list filter on one Title", trainingCrs); 

Answer 3

loadCategories(){ 
        let categs = _categories,
            trainingCrs = _categories.d.results.map((x) =>x.Courses.results.Title)
            });