Server-Side Scripting/Associative Arrays/Node.js (Express)
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routes/lesson7.js
[edit | edit source]// This program reads a user-selected text file of countries
// and Celsius temperatures. It displays the data in Celsius
// and Fahrenheit sorted in descending order by temperature.
//
// File format:
// Country,MaximumTemperature
// Bulgaria,45.2 °C
// Canada,45 °C
//
// https://www.mathsisfun.com/temperature-conversion.html
// https://en.wikibooks.org/wiki/JavaScript
// https://www.npmjs.com/package/express-fileupload
const express = require('express')
const fs = require("fs");
const handlebars = require('handlebars');
const router = express.Router()
router.get("/", function (request, response) {
let source = fs.readFileSync("./templates/lesson7.html");
let template = handlebars.compile(source.toString());
let data = {
table: ""
}
result = template(data);
response.send(result);
});
router.post("/", function (request, response) {
let result = "";
if (!request.files || Object.keys(request.files).length == 0) {
result = "No file selected"
} else {
let file = request.files.file;
result += "<h2>" + file.name + "</h2>";
result += processFile(file)
}
let source = fs.readFileSync("./templates/lesson7.html");
let template = handlebars.compile(source.toString());
let data = {
table: result
}
result = template(data);
response.send(result);
});
function processFile(file) {
let text = file.data.toString();
let lines = text.trim().split("\n");
if (lines[0].toLowerCase().indexOf("country") >= 0) {
// remove heading line
lines.shift();
}
let table = [];
for (let index = 0; index < lines.length; index++) {
try {
let record = processLine(lines[index]);
table.push(record);
}
catch(error) {
return error;
}
}
table.sort(function(a, b) {return b.celsius - a.celsius});
result = formatTable(table);
return result
}
function processLine(line) {
let record = {};
let array = line.split(",");
if (array.length != 2) {
throw "Invalid file format"
}
record.country = array[0];
let celsius = array[1];
let index = celsius.indexOf(" °C");
if (index < 0) {
throw "Invalid file format";
}
celsius = Number(celsius.substring(0, index));
record.celsius = celsius;
let fahrenheit = celsius * 9 / 5 + 32;
record.fahrenheit = fahrenheit
return record;
}
function formatTable(table) {
let result = "<table><tr><th>Country</th>"
result += "<th>Celsius</th>";
result += "<th>Fahrenheit</th></tr>";
for (index = 0; index < table.length; index++) {
let record = table[index];
result += "<tr><td>" + record.country + "</td>";
result += "<td>" + record.celsius.toFixed(1) + "° C</td>";
result += "<td>" + record.fahrenheit.toFixed(1) + "° F</td></tr>";
}
result += "</table>";
return result;
}
module.exports = router;
templates/lesson7.html
[edit | edit source]<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Lesson 7</title>
<link rel="stylesheet" href="styles.css">
<style>
p {
min-height: 1em;
}
</style>
</head>
<body>
<h1>Temperature Conversion</h1>
<p>Select a file of Fahrenheit temperatures for conversion:</p>
<form method="POST" enctype="multipart/form-data">
<input type="file" id="file" name="file">
<input type="submit">
</form>
{{{table}}}
</body>
</html>
Try It
[edit | edit source]See Server-Side Scripting/Routes and Templates/Node.js (Express) to create a test environment.
See Server-Side Scripting/Strings and Files/Node.js (Express) for app.js content.