js使用for循环输出直角三角形、等腰三角形、菱形、对角线菱形、空心菱形

1.直角三角形

*

*

*  *    1  2  1 

*  ***    2  1  3

* *****  3  0  5  空格数量：n - i 2*n - 1

*

 function printStar(layer) {

                     var str = "";

                     for (var i = 0; i < layer; i++) {

                             for (var j = 0; j <= i; j++) {

                                             str += "*"

                               }

                                     str += "\n";

                        }

                         console.log(str)

         }

         printStar(10);

2.等腰三角形：

 function printStar2(layer) {

             var str = "";

             for (var i = 1; i <= layer; i++) {

                    var spaceNum = layer - i;

                    for (var j = 0; j < spaceNum; j++) {

                                str += " ";

                    }

                     var starNum = 2*i - 1;

                     for (var j = 0; j < starNum; j++) {

                         str += "*";

                       }

                         str += "\n";

                 }

                 console.log(str);

     }

 printStar2(10);

3.菱形：

function printStar2(layer) {

         var str = "";

         for (var i = 1; i <= layer; i++) {

                 var spaceNum = layer - i;

                 for (var j = 0; j < spaceNum; j++) {

                                 str += " ";

                     }

                   var starNum = 2*i - 1;

                    for (var j = 0; j < starNum; j++) {

                                 str += "*";

                       }

                     str += "\n";

             }

         for (var i = layer - 1; i >= 0; i--) {

                 var spaceNum = layer - i;

                 for (var j = 0; j < spaceNum; j++) {

                                 str += " ";

                     }

                 var starNum = 2*i - 1;

                             for (var j = 0; j < starNum; j++) {

                                         str += "*";

                             }

                             str += "\n";

                        }

                     console.log(str);

       }

 printStar2(10);

4.对角线菱形：

function printStar2(layer) {

            var str = "";

            for (var i = 1; i <= layer; i++) {

                            var spaceNum = layer - i;

                            for (var j = 0; j < spaceNum; j++) {

                                                    str += " ";

                            }

                            var starNum = 2*i - 1;

                            for (var j = 0; j < starNum; j++) {

                                    if (i == layer) {

                                                    str += "*";

                                    } else {

                                                    if (j == 0 || j == starNum -1 || j == (i -1)) {

                                                                    str += "*";

                                                      } else {

                                                                    str += " ";

                                                                    }

                                                    }

                                        }

                                            str += "\n";

                                    }

                                    for (var i = layer - 1; i >= 0; i--) {

                                                        var spaceNum = layer - i;

                                                        for (var j = 0; j < spaceNum; j++) {

                                                                                            str += " ";

                                                            }

                                                            var starNum = 2*i - 1;

                                                            for (var j = 0; j < starNum; j++) {

                                                                        if (j == 0 || j == starNum -1 || j == (i -1)) {

                                                                                          str += "*";

                                                                           } else {

                                                                                        str += " ";

                                                                                        }

                                                                              }

                                                                                str += "\n";

                                                             }

                                                            console.log(str);

                                         }

                                        printStar2(10);

5.空心菱形

function printStar2(layer) {

                    var str = "";

                     for (var i = 1; i <= layer; i++) {

                                    var spaceNum = layer - i;

                                      for (var j = 0; j < spaceNum; j++) {

                                                        str += " ";

                                            }

                                        var starNum = 2*i - 1;

                                        for (var j = 0; j < starNum; j++) {

                                                        if(j == 0|| j == starNum-1){

                                                                                    str += "*";

                                                            }else{

                                                                    str += " ";

                                                            }

                                                        }

                                                        str += "\n";

                                }        

                                for (var i = layer - 1; i >= 0; i--) {

                                                    var spaceNum = layer - i;

                                                    for (var j = 0; j < spaceNum; j++) {

                                                                            str += " ";

                                                        }

                                                    var starNum = 2*i - 1;

                                                    for (var j = 0; j < starNum; j++) {

                                                                    if(j == 0|| j == starNum-1){

                                                                                        str += "*";

                                                                    }else{

                                                                                            str += " ";

                                                                        }

                                                        }

                                                        str += "\n";

                                               }

                                                console.log(str);

                 }

                printStar2(10);