js functional programming examples

loiane · loiane · commit b008a7264913 · 2016-04-02T12:16:27.000-03:00
diff --git a/chapter11/12-IntroFunctionalProgramming.html b/chapter11/12-IntroFunctionalProgramming.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title></title>
+</head>
+<body>
+<script src="12-IntroFunctionalProgramming.js"></script>
+</body>
+</html>
diff --git a/chapter11/12-IntroFunctionalProgramming.js b/chapter11/12-IntroFunctionalProgramming.js
@@ -0,0 +1,147 @@
+console.log('Using imperative JS');
+
+var printArray = function(array){
+    for (var i=0; i<array.length; i++){
+        console.log(array[i]);
+    }
+};
+
+printArray([1, 2, 3, 4, 5]);
+
+//how can we abstract the For flow? Can we use a callback for action?
+
+console.log('Using functional JS');
+
+var forEach = function(array, action){
+    for (var i=0; i<array.length; i++){
+        action(array[i]);
+    }
+};
+
+var logItem = function (item) {
+    console.log(item);
+};
+
+forEach([1, 2, 3, 4, 5], logItem);
+
+//how can we abstract the For flow?
+console.log('Finding the min value in an array - imperative');
+
+var findMinArray = function(array){
+    var minValue = array[0];
+    for (var i=1; i<array.length; i++){
+        if (minValue > array[i]){
+            minValue = array[i];
+        }
+    }
+
+    return minValue;
+};
+
+console.log(findMinArray([8,6,4,5,9]));
+
+console.log('Finding the min value in an array - functional ES2015');
+const min_ = function(array){
+    return Math.min(...array)
+};
+
+//simplifying using arrow functions
+const min = arr => Math.min(...arr);
+
+console.log(min_([8,6,4,5,9]));
+console.log(min([8,6,4,5,9]));
+
+//concat + reduce
+console.log('merge arrays - imperative');
+
+var mergeArrays_ = function(arrays){
+    var count = arrays.length,
+        newArray = [],
+        k =0;
+    for (var i=0; i<count; i++){
+        for (var j=0; j<arrays[i].length; j++){
+            newArray[k++] = arrays[i][j];
+        }
+    }
+    return newArray;
+};
+
+console.log(mergeArrays_([[1, 2, 3], [4, 5], [6]]));
+
+console.log('merge arrays - using concat');
+var mergeArraysConcat = function(arrays){
+    return arrays.reduce( function(p,n){
+        return p.concat(n);
+    });
+};
+
+console.log(mergeArraysConcat([[1, 2, 3], [4, 5], [6]]));
+
+console.log('merge arrays - ES2015');
+
+const mergeArrays = (...arrays) => [].concat(...arrays);
+console.log(mergeArrays([1, 2, 3], [4, 5], [6]));
+
+console.log('sum values of arrays - imperative');
+var sumValues = function(array){
+    var total = array[0];
+    for (var i=1; i<array.length; i++){
+        total += array[i];
+    }
+    return total;
+};
+
+console.log(sumValues([1, 2, 3, 4, 5]));
+
+//reduce
+console.log('sum values of arrays - functional');
+var sum_ = function(array){
+    return array.reduce(function(a, b){
+        return a + b;
+    })
+};
+
+console.log(sum_([1, 2, 3, 4, 5]));
+
+console.log('sum values of arrays - ES2015');
+const sum = arr => arr.reduce((a, b) => a + b);
+
+console.log(sum([1, 2, 3, 4, 5]));
+
+//map
+var daysOfWeek = [
+    {name: 'Monday', value: 1},
+    {name: 'Tuesday', value: 2},
+    {name: 'Wednesday', value: 7}
+];
+
+var daysOfWeekValues_ = [];
+for (var i = 0; i < daysOfWeek.length; i++) {
+    daysOfWeekValues_.push(daysOfWeek[i].value);
+}
+
+//to
+var daysOfWeekValues = daysOfWeek.map(function(day) {
+    return day.value;
+});
+console.log(daysOfWeekValues);
+
+
+//filter
+var positiveNumbers_ = function(array){
+    var positive = [];
+    for (var i = 0; i < array.length; i++) {
+        if (array[i] >= 0){
+            positive.push(array[i]);
+        }
+    }
+    return positive;
+}
+console.log(positiveNumbers_([-1,1,2,-2]));
+
+var positiveNumbers = function(array){
+    return array.filter(function(num){
+        return num >= 0;
+    })
+};
+console.log(positiveNumbers([-1,1,2,-2]));
