Test writer dev branch

.gitignore

@@ -0,0 +1 @@
+node_modules/

inventory.js

@@ -0,0 +1,164 @@
+
+function calculateDiscount(price = 0, discountRate = 0.0) 
+{
+    let returnValue;
+
+    try
+    {
+        if (typeof price !== "number")
+        {
+            returnValue = null;
+
+            throw new Error("Price must be a number.");
+        } 
+
+        if (price < 0)
+        {
+            returnValue = 0;
+
+            throw new Error("Price must be greater than 0.");
+        }
+
+        if (typeof discountRate !== 'number') 
+        {
+            returnValue = price;
+
+            throw new Error("Discount rate must be a number.");
+        }
+
+        if (discountRate < 0)
+        {
+            returnValue =  price;
+
+            throw new Error("Discount rate must be great than 0.");
+        } 
+
+        if (discountRate > 1) 
+        {
+            returnValue = price;
+
+            throw new Error("Discount rate must be less than 100%.");
+        }
+
+        return price * (1 - discountRate);
+
+    }
+
+    catch (err)
+    {
+        console.error(`Error: ${err.message}`);
+
+        return returnValue;
+    }
+}
+
+
+function filterProducts(products, callback) 
+{
+    try
+    {
+        if (!Array.isArray(products)) 
+        {
+            throw new Error("Products must be an array.");
+        }
+
+        if (typeof callback !== 'function')
+        {
+            throw new Error("Callback must be a function.");
+        }
+
+        return products.filter(callback);
+    }
+
+    catch (err)
+    {
+        console.error(`Error: ${err.message}`);
+
+        return [];
+    }
+}
+
+
+function sortInventory(inventory = [], key = "") 
+{
+    let returnValue;
+
+    try
+    {
+        if (!Array.isArray(inventory))
+        {
+            returnValue = [];
+
+            throw new Error("Inventory must be an array.");    
+        }
+
+        if (inventory.length === 0)
+        {
+            return [];
+        }
+
+        if (typeof key !== 'string')
+        {
+            returnValue = inventory;
+
+            throw new Error("Key must be a string.");
+        }
+
+        if (!key)
+        {
+            returnValue = inventory;
+
+            throw new Error("No key was provided.");
+        }
+
+        if (key.trim() === "")
+        {
+            returnValue = inventory;
+
+            throw new Error("Blank key was provided.");
+        }
+
+        let foundKey = false;
+
+        for (let keyName in inventory[1])
+        {  
+            if (keyName === key)
+            {
+                foundKey = true;
+                break;
+            }
+        }
+
+        if (!foundKey)
+        {
+            returnValue = inventory;
+
+            throw new Error("Key not found in object.");
+        }
+
+        if (key === "price" || key === "inStock")
+        { 
+            return inventory.sort((a, b) => a[key] - b[key]);
+        }
+        else if (key === "name")
+        {
+            return inventory.sort((a, b) => a[key].toLowerCase().localeCompare(b[key].toLowerCase()));
+        }
+    }
+
+    catch (err)
+    {
+        console.error(`Error: ${err.message}`);
+
+        return returnValue;
+    }
+}
+
+
+module.exports = 
+{
+    calculateDiscount: calculateDiscount,
+    filterProducts: filterProducts,
+    sortInventory: sortInventory
+};
+