Alex Alex - 3 months ago 19
Javascript Question

Function invocation for a random category pickup [solved]

I need a help for educational task.
I just have started JS learning and my knowledge is not sufficient for such task..
The problem: what may I pass into chooseRandomCategory() function (STEP 2) for HTML-page generating with random Category?
Please, give me advice how to solve it.



(function (global) {
var dc = {};
var homeHtmlUrl = "snippets/home-snippet.html";
var allCategoriesUrl =
"https://davids-restaurant.herokuapp.com/categories.json";
var categoriesTitleHtml = "snippets/categories-title-snippet.html";
var categoryHtml = "snippets/category-snippet.html";
var menuItemsUrl =
"https://davids-restaurant.herokuapp.com/menu_items.json?category=";
var menuItemsTitleHtml = "snippets/menu-items-title.html";
var menuItemHtml = "snippets/menu-item.html";

// Convenience function for inserting innerHTML for 'select'
var insertHtml = function (selector, html) {
var targetElem = document.querySelector(selector);
targetElem.innerHTML = html;
};

// Return substitute of '{{propName}}'
// with propValue in given 'string'
var insertProperty = function (string, propName, propValue) {
var propToReplace = "{{" + propName + "}}";
string = string
.replace(new RegExp(propToReplace, "g"), propValue);
return string;
}

// On page load (before images or CSS)
document.addEventListener("DOMContentLoaded", function (event) {

// TODO: STEP 0: Look over the code from
// *** start ***
// to
// *** finish ***
// below.
// We changed this code to retrieve all categories from the server instead of
// simply requesting home HTML snippet. We now also have another function
// called buildAndShowHomeHTML that will receive all the categories from the server
// and process them: choose random category, retrieve home HTML snippet, insert that
// random category into the home HTML snippet, and then insert that snippet into our
// main page (index.html).
//
// TODO: STEP 1: Substitute [...] below with the *value* of the function buildAndShowHomeHTML,
// so it can be called when server responds with the categories data.

// *** start ***
// On first load, show home view
showLoading("#main-content");
$ajaxUtils.sendGetRequest(
allCategoriesUrl,
buildAndShowHomeHTML, // ***** <---- TODO: STEP 1: Substitute [...] ******
true); // Explicitely setting the flag to get JSON from server processed into an object literal
});
// *** finish **

// Builds HTML for the home page based on categories array
// returned from the server.
function buildAndShowHomeHTML (categories) {

// Load home snippet page
$ajaxUtils.sendGetRequest(
homeHtmlUrl,
function (homeHtml) {

// TODO: STEP 2: Here, call chooseRandomCategory, passing it retrieved 'categories'
// Pay attention to what type of data that function returns vs what the chosenCategoryShortName
// variable's name implies it expects.
var chosenCategoryShortName = chooseRandomCategory(???);

// TODO: STEP 3: Substitute {{randomCategoryShortName}} in the home html snippet with the
// chosen category from STEP 2. Use existing insertProperty function for that purpose.
// Look through this code for an example of how to do use the insertProperty function.
// WARNING! You are inserting something that will have to result in a valid Javascript
// syntax because the substitution of {{randomCategoryShortName}} becomes an argument
// being passed into the $dc.loadMenuItems function. Think about what that argument needs
// to look like. For example, a valid call would look something like this:
// $dc.loadMenuItems('L')
// Hint: you need to surround the chosen category short name with something before inserting
// it into the home html snippet.
//

var homeHtmlToInsertIntoMainPage = insertProperty(homeHtml, "randomCategoryShortName", chosenCategoryShortName);

// TODO: STEP 4: Insert the the produced HTML in STEP 3 into the main page
// Use the existing insertHtml function for that purpose. Look through this code for an example
// of how to do that.

insertHtml("#main-content", homeHtmlToInsertIntoMainPage);
},
false); // False here because we are getting just regular HTML from the server, so no need to process JSON.
}

// Given array of category objects, returns a random category object.
function chooseRandomCategory (categories) {
// Choose a random index into the array (from 0 inclusively until array length (exclusively))
var randomArrayIndex = Math.floor(Math.random() * categories.length);

// return category object with that randomArrayIndex
return categories[randomArrayIndex];
}

global.$dc = dc;

})(window);




Answer

Solved in a such way:

// TODO: STEP 2: Here, call chooseRandomCategory, passing it retrieved 'categories'
      // Pay attention to what type of data that function returns vs what the chosenCategoryShortName
      // variable's name implies it expects.
      var chosenCategoryShortName = chooseRandomCategory(categories);
      
      // TODO: STEP 3: Substitute {{randomCategoryShortName}} in the home html snippet with the
      // chosen category from STEP 2. Use existing insertProperty function for that purpose.
      // Look through this code for an example of how to do use the insertProperty function.
      // WARNING! You are inserting something that will have to result in a valid Javascript
      // syntax because the substitution of {{randomCategoryShortName}} becomes an argument
      // being passed into the $dc.loadMenuItems function. Think about what that argument needs
      // to look like. For example, a valid call would look something like this:
      // $dc.loadMenuItems('L')
      // Hint: you need to surround the chosen category short name with something before inserting
      // it into the home html snippet.
      // 

      var homeHtmlToInsertIntoMainPage = insertProperty(homeHtml, "randomCategoryShortName", "'" + chosenCategoryShortName.short_name + "'");