Advanced-JavaScript-With-Projects/nestedForLoop.html at main · marleyDip/Advanced-JavaScript-With-Projects · GitHub

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Nested For Loop</title>
  </head>
  <body></body>
  <script>
    // Logic is equal to magic

    // row
    for (let row = 1; row <= 5; row++) {
      // column
      for (let r = 1; r <= 5; r++) {
        document.write("*");
      }
      document.write("<br />");
    }

    // Row = outside Loop
    for (let r = 1; r <= 5; r++) {
      // Column = inside loop
      for (let i = 1; i <= r; i++) {
        document.write("*");
      }

      // first print row 1, row 2, row 3, row 4, row 5

      // when (row) outside 1 enter inside (column) loop,  then --> r = 1, i = 1

      // when (row) outside 2 enter inside (column) loop,  then --> r = 2, i = 1
      // r =2, i = 2

      document.write("<br />");
    }

    for (let r = 5; r >= 1; r--) {
      for (let i = 1; i <= r; i++) {
        document.write("*");

        // i continue print * = 5 times bcz i <= r

        // after i = 4 times bcz i <= 4

        // first print row 5, row 4, row 3, row 2, row 1

        // when (row) outside 5 enter inside (column) loop,  then --> r = 5, i = 1
        // --> r = 5, i = 2
        // --> r = 5, i = 3
        // --> r = 5, i = 4
        // --> r = 5, i = 5

        // execution complete, then execute break// when (row) outside 4 enter inside (column) loop,  then --> r = 4, i = 1
        // --> r = 4, i = 2
        // --> r = 4, i = 3
        // --> r = 4, i = 4

        // --> r = 5, i = 5  x => its not valid bcz i <= r; 5 <= 4; condition false

        // execution complete, then execute break

        // ..... continue too, it comes r = 1, i =1
      }
      document.write("<br />");
    }

    // row
    for (let row = 1; row <= 5; row++) {
      // column
      for (let r = 1; r <= row; r++) {
        document.write(r);
      }
      document.write("<br />");
    }

    // row
    for (let row = 5; row >= 1; row--) {
      // column
      for (let r = 1; r <= row; r++) {
        document.write(r);
      }
      document.write("<br />");
    }
  </script>
</html>