Cont'd Day1, started functional programming, still need to finish reading and start exercises

solutions/day-01/functional_programming/script.js

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+// functional progamming allow for writing shorter and cleaner code. 
+// You can also solve more complicated problems that are difficult to solve 
+// via tradional methods
+
+// 1. forEach
+// -  use it to iterate through array of items. 
+// -  use it if you are interested in each item or index or both.
+const countries = ['Finland', 'Estonia', 'Sweden', 'Norway'];
+countries.forEach((element, index, array) => {
+    console.log(index, element.toUpperCase());
+});
+
+// 2. map
+// use map method when we like to modify an array. 
+// use only on arrays, and map method always returns an array
+const cities = ['Austin', 'Houston', 'Dallas', 'Galveston', 'Lubbock'];
+const uppercase = cities.map(element =>{
+    return element.toUpperCase();
+});
+console.log(uppercase);
+
+// 3. filter
+// - used with arrays
+// - returns and array of filtered items
+const food = ['Pizza', 'Grapes', 'Cake', 'Milk', 'pasta' ,'Flour', 'Tea', 'Pumpkin'];
+const filteredFood = food.filter(item => {
+    return item.charAt(0) == 'P' || item.charAt(0) == 'p';
+})
+console.log(filteredFood);
+
+// 4. reduce
+// - used with arrays
+// - returns a single value
+// - used to sum all numbers in an array together, or contcate items, or multiply items, etc.
+const nums = [10,2,16,9,55,6];
+const sum = nums.reduce((a,b)=>{ return a+b});
+console.log(sum);
+
+// 5. find
+// - looks for first occurence of a certain array element.
+// returns first item that passes a test
+const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+const found = numbers.find((element)=>{ return element > 4 && element < 8});
+console.log(found);
+
+