Learn API's for Students

expressapis.js

import express from "express";
const app = express();

app.use(express.json());

// 1️⃣ Add two numbers
app.post("/add", (req, res) => {
  const { a, b } = req.body;
  res.json({ result: a + b });
});

// 2️⃣ Multiply numbers
app.post("/multiply", (req, res) => {
  const { x, y } = req.body;
  res.json({ result: x * y });
});

// 3️⃣ Compare numbers
app.post("/compare", (req, res) => {
  const { x, y } = req.body;
  if (x > y) return res.json({ result: "x is greater" });
  if (y > x) return res.json({ result: "y is greater" });
  res.json({ result: "both are equal" });
});

// 4️⃣ Even or Odd
app.post("/even-odd", (req, res) => {
  const { num } = req.body;
  res.json({ result: num % 2 === 0 ? "even" : "odd" });
});

// 5️⃣ Reverse String
app.post("/reverse", (req, res) => {
  const { text } = req.body;
  res.json({ result: text.split("").reverse().join("") });
});

// 6️⃣ Palindrome Check
app.post("/palindrome", (req, res) => {
  const { text } = req.body;
  const reversed = text.split("").reverse().join("");
  res.json({ result: text === reversed ? "palindrome" : "not palindrome" });
});

// 7️⃣ Vowel Count
app.post("/vowels", (req, res) => {
  const { text } = req.body;
  const count = text.match(/[aeiouAEIOU]/g)?.length || 0;
  res.json({ result: count });
});

// 8️⃣ Age Eligibility
app.post("/eligibility", (req, res) => {
  const { age } = req.body;
  res.json({ result: age >= 18 ? "eligible" : "not eligible" });
});

// 9️⃣ Max from Array
app.post("/max", (req, res) => {
  const { numbers } = req.body;
  res.json({ result: Math.max(...numbers) });
});

// 🔟 Celsius → Fahrenheit
app.post("/temperature", (req, res) => {
  const { c } = req.body;
  const f = (c * 9) / 5 + 32;
  res.json({ result: f });
});

// =============================
// Bonus +10 APIs
// =============================

// 1️⃣1️⃣ Age Calculator
app.post("/age", (req, res) => {
  const { birthYear } = req.body;
  const currentYear = new Date().getFullYear();
  res.json({ result: currentYear - birthYear });
});

// 1️⃣2️⃣ Square of Number
app.post("/square", (req, res) => {
  const { num } = req.body;
  res.json({ result: num * num });
});

// 1️⃣3️⃣ Simple Interest
app.post("/simple-interest", (req, res) => {
  const { p, r, t } = req.body;
  const si = (p * r * t) / 100;
  res.json({ result: si });
});

// 1️⃣4️⃣ Area of Circle
app.post("/circle-area", (req, res) => {
  const { radius } = req.body;
  const area = 3.14 * radius * radius;
  res.json({ result: area });
});

// 1️⃣5️⃣ Grade Calculator
app.post("/grade", (req, res) => {
  const { marks } = req.body;
  let grade = "";
  if (marks >= 90) grade = "A";
  else if (marks >= 75) grade = "B";
  else if (marks >= 50) grade = "C";
  else grade = "Fail";
  res.json({ result: grade });
});

// 1️⃣6️⃣ Convert to Uppercase
app.post("/upper", (req, res) => {
  const { text } = req.body;
  res.json({ result: text.toUpperCase() });
});

// 1️⃣7️⃣ Convert to Lowercase
app.post("/lower", (req, res) => {
  const { text } = req.body;
  res.json({ result: text.toLowerCase() });
});

// 1️⃣8️⃣ Minimum from Array
app.post("/min", (req, res) => {
  const { numbers } = req.body;
  res.json({ result: Math.min(...numbers) });
});

// 1️⃣9️⃣ Positive or Negative
app.post("/sign", (req, res) => {
  const { num } = req.body;
  res.json({ result: num > 0 ? "positive" : num < 0 ? "negative" : "zero" });
});

// 2️⃣0️⃣ String Length
app.post("/length", (req, res) => {
  const { text } = req.body;
  res.json({ result: text.length });
});

// 🚀 Server Start
app.listen(5000, () => {
  console.log("Server running at http://localhost:5000");
});