Question

你好，我遇到了这个功能的问题。我想创建一个函数，它接受一个数字，一个起点和一个终点，然后写出从起点到终点的数字乘法表。例如，tabmul（10,2,4）返回

10.2 = 20

10.3 = 30

10.4 = 40

这一切都很好，但它对负数并不起作用。例如， tabmul（10，-4，-1）应生成

10.-4 = -40

10.-3 = -30

10.-2 = -20

10.-1 = -10

但它没有返回任何东西。这是我的代码：

function tabmul(a,b,c){ \\function that generates the multiplication table
    var myarray = new Array();
    var x
    for(x=b; x<=c; x++){
        myarray[x - b] = a*x;
        document.write(a + "." + x + "=" + myarray[x - b] + "<br>")
    }
}
var a = prompt("Enter the number whose table you want to calculate: ","");
var b = prompt("Enter the place where you want the table to start","");
var c = prompt("Enter the place where you want the table to end","");
\\ this checks if the starting point is smaller or equal than the ending point of the table
if (0 <= c-b) {
  tabmul(a,b,c);

} else {
    alert("The starting point is bigger than the ending point");
}

Answer 1

您正在比较字符串。这是因为提示返回字符串。您需要将a,b,c转换为数字。此外，您使用错误的符号进行评论，您需要更正这些符号。

function tabmul(a,b,c){ //function that generates the multiplication table
    a = Number(a);
    b = Number(b);
    c = Number(c);
    var myarray = new Array();
    var x
    for(x=b;x<=c;x++){
        myarray[x-b] = a*x;
        document.write(a+"."+x+"="+myarray[x-b]+"<br/>")
    }
}
var a = prompt("Enter the number whose table you want to calculate: ","");
var b = prompt("Enter the place where you want the table to start","");
var c = prompt("Enter the place where you want the table to end","");
if(0 <= c-b){ //this checks if the starting point is smaller or equal than the ending point of the table
tabmul(a,b,c);
}
else{
    alert("The starting point is bigger than the ending point");
}

Answer 2

您还应该使用Number或parseInt将输入转换为数字，以确保其为数字。

之后，您可能会遇到使用负数引用索引数组的问题。

myarray[x-b] // can fail if x-b<0. Also for a large number n it will insert empty elements in your array up to N.

例如，请采取以下措施：

var myarray= new Array();
myarray[-4]=1;
console.log(JSON.stringify(myarray));
// result "[]"
myarray= new Array();
myarray[10]=1;
console.log(JSON.stringify(myarray));
// result "[null,null,null,null,null,null,null,null,null,null,1]"

您可以将其转换为字符串：

myarray['"' + (x-b) + '"'] = a*x;

或者您可以使用push（），索引将从零开始。：

 for(x=b;x<=c;x++){
    myarray.push(a*x);
    document.write(a+"."+x+"="+myarray(myarray.length-1)+"<br/>")
}

Answer 3

1）为函数参数设置正常名称 2）使用缩进和＆＃39;让＆＃39;在＆＃39;为＆＃39;循环而不是＆＃39; var＆＃39;就在之前：

for(let x = b; x <= c; x++){}

3）不要忘记分号。

function multiplication(val, start, end) {
  if(end - start <= 0) return;
  for(let i = start; i <= end; i++) {
    console.log(val + ' * ' + i + ' = ' + val * i);
  }
}
multiplication(10, -4, -1);

10 * -4 = -40
10 * -3 = -30
10 * -2 = -20
10 * -1 = -10

返回乘法表的函数失败，带负数

3 个答案: