JavaScript-Concepts/recursion.html at master · kipchirchiralb/JavaScript-Concepts · GitHub

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<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <title>Recursion</title>
</head>

<body>
    <h1>Recursion</h1>
    <p>a function that calls itself</p>
    <p>It is a way of solviving problems where a solution uses a solution from another smaller instance of the same problem</p>

    <script>
        //non-recursive count down from n to 0
        function countDown(n) {
            for (let i = n; i > 0; i--) {
                console.log(i)
            }
            console.log("Go!! non-recursive")
        }
        countDown(5)

        //recursive countdown
        function countDownRecursive(n) {
            if (n <= 0) {
                console.log("Go!! Recursive!")
                return
            }
            console.log(n)
            countDownRecursive(n - 1) //the function calling itself
        }
        countDownRecursive(10)

        //sum a range of numbers - non-recursive
        function sumRange(n) {
            let total = 0
            for (let i = n; i > 0; i--) {
                total += i

            }
            console.log(`${total} is the total from a non-recursive`)
        }
        sumRange(5)

        //sum of a range of numbers - recursive
        function sumRangeRecursive(n, total = 0) {
            if (n <= 0) {
                return total
            }
            return sumRangeRecursive(n - 1, total + n)
        }
        console.log(`${sumRangeRecursive(5)} is the total of sum of a range from a recursive`)

        //a more dedicated way of using recursion

        function printChildren(t) {}

        function printChildrenRecursive(t) {
            if (t.children.length === 0) {
                return
            }
            t.children.forEach(child => {
                console.log(child.name)
                printChildrenRecursive(child)
            });
        }

        const tree = {
            name: "John",
            children: [{
                name: "Kyle",
                children: []
            }, {
                name: "Kim",
                children: [{
                    name: "joung",
                    children: []
                }, {
                    name: "Hu",
                    children: []
                }]
            }]
        }

        printChildrenRecursive(tree)
    </script>
</body>

</html>