Prepare good and bad imperative style examples

Author: tshemsedinov

JavaScript/1-imperative-bad.js

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+'use strict';
+
+// 1. Control flow
+// 2. Step by step execution
+// 3. Assignment statements
+// 4. Loops and conditions: for/if
+// 5. State variables and side effects
+// 6. Mutable data structures
+// 7. Model of the process
+
+const fs = require('fs');
+
+const data = fs.readFileSync('./cities.dat');
+if (data) {
+ const lines = data.toString().split('\n');
+ lines.pop();
+ const table = [];
+ let first = true;
+ let max = 0;
+ for (const line of lines) {
+ if (first) {
+ first = false;
+ } else {
+ const cells = line.split(',');
+ const d = parseInt(cells[3]);
+ if (d > max) max = d;
+ table.push([cells[0], cells[1], cells[2], cells[3], cells[4]]);
+ }
+ }
+ for (const row of table) {
+ const a = Math.round(row[3] * 100 / max);
+ row.push(a.toString());
+ }
+ table.sort((r1, r2) => r2[5] - r1[5]);
+ for (const row of table) {
+ let s = row[0].padEnd(18);
+ s += row[1].padStart(10);
+ s += row[2].padStart(8);
+ s += row[3].padStart(8);
+ s += row[4].padStart(18);
+ s += row[5].padStart(6);
+ console.log(s);
+ }
+}

JavaScript/1-imperative-good.js

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+'use strict';
+
+// 1. Control flow
+// 2. Step by step execution
+// 3. Assignment statements
+// 4. Loops and conditions: for/if
+// 5. State variables and side effects
+// 6. Mutable data structures
+// 7. Model of the process
+
+const fs = require('fs');
+
+function loadFile(fileName) {
+ let data = null;
+ try {
+ data = fs.readFileSync(fileName);
+ } catch (error) {
+ console.log('Can\'t read file: ' + fileName);
+ }
+ return data;
+}
+
+function parseFile(data) {
+ const lines = data.toString().split('\n');
+ lines.shift();
+ const cities = [];
+ for (const line of lines) {
+ if (line) {
+ const cells = line.split(',');
+ const name = cells[0];
+ const population = parseInt(cells[1]);
+ const area = parseInt(cells[2]);
+ const density = parseInt(cells[3]);
+ const country = cells[4];
+ cities.push({ name, population, area, density, country });
+ }
+ }
+ return cities;
+}
+
+function calculateDensityColumn(cities) {
+ cities.sort((city1, city2) => city2.density - city1.density);
+ const maxDensity = cities[0].density;
+ for (const city of cities) {
+ city.relative = Math.round(city.density * 100 / maxDensity);
+ }
+}
+
+function showTable(cities) {
+ for (const city of cities) {
+ const line = (
+ city.name.padEnd(18) +
+ city.population.toString().padStart(10) +
+ city.area.toString().padStart(8) +
+ city.density.toString().padStart(8) +
+ city.country.padStart(18) +
+ city.relative.toString().padStart(6)
+ );
+ console.log(line);
+ }
+}
+
+const data = loadFile('./cities.dat');
+if (data) {
+ const cities = parseFile(data);
+ calculateDensityColumn(cities);
+ showTable(cities);
+}