如何在JavaScript中打印雷电星型？

Question

我有一项任务要做雷电星型循环，如下所示：

*
 *
  *
   *
****
*
 *
  *
   *

我只能做到这一部分：

​

$n = 5;
for($i = 1; $i <= $n; $i++) {
 for($j = 1; $j <= $n; $j++) {
  if($i == $j) {
    document.write(" * ");
  } 
  else {
    document.write("&nbsp;&nbsp;&nbsp;");
  }
}
  document.write("<br/>");
}

​

Answer 1

可以通过增加一个变量来实现模式的循环。

​

$n = 5;
$count = 1; // added for looping pattern
for($i = 0; $i <= $n; $i++) {
 for($j = 1; $j <= $i; $j++) {
  if($i == $j&& $i != $n ) {
    document.write(" * ");
  }if($i == $n && $j < $n && $count > 0){
   document.write(" * ");
  }else {
    document.write("&nbsp;&nbsp;&nbsp;");
  }
}
if($i == $n && $j == ($n + 1 ) && $count > 0)
  {
   $j=1;
   $i=0;
   $count--;
  }
  document.write("<br/>");
}

​

Answer 2

​

const diagonalLine = (n) => {
  let line = '';

  for (let i = 0; i < n; i++) {
    for (let j = 0; j < i; j++) {
      line += ' ';
    }
    line += '*\n';
  }
  return line;
};
const line = (n) => {
  let line = '';

  for (let i = 0; i < n; i++) {
    line += '*';
  }
  return line;
};
const printPattern = n => `${diagonalLine(n)}${line(n)}${diagonalLine(n)}`;

console.log(printPattern(5));

​