JSS作业：

1:

<script>var cnt = parseInt(window.prompt("请输入打印的行数："));for (var i = 1; i <= cnt; i++){for (var j = 1; j <= i; j++){document.write("*")}document.write("<br>")}
</script>

2:

<script>let cnt = parseInt(prompt("请输入要打印的行数："));for(var i=1;i<=cnt;i++){for(var j=1;j<=cnt-i;j++){document.write("&nbsp;");}for(var j=1;j<=2*i-1;j++){document.write("*");}document.write("<br/>");}
</script>

3:

<script>let cnt = parseInt(prompt("请输入要打印的行数："));for(var i=0; i<cnt; i++){       for(var j=cnt; j>i; j--){document.write("&nbsp");}      for(var k=0;k<2*i+1;k++){document.write("*");}      document.write("</br>");}for(var i=cnt-1; i>0; i--){for(var j=cnt; j>=i; j--){document.write("&nbsp");}   for(var k=0; k<2*i-1; k++){document.write("*");}document.write("</br>")}
</script>

4:

<script>var num=0;for(var i=1; i<10; i++){for(var j=1; j<10; j++){num = i * j;if(num / 10 < 1){num="&nbsp;&nbsp;" + i * j;}if(j<=i) {document.write(j + "*" + i + "=" + num + "&nbsp;&nbsp;&nbsp;&nbsp;");}}   document.write("<br>");}
</script>