Question

我想在我的代码中限制符号，负数和所有其他非相关内容。我的教授告诉我使用isNaN，但我不知道如何在我的代码中应用。有人可以帮我解决这个问题吗？我在下面附上了我的代码

<!-- Network Latency Calculator -->

<html>
<head>
  <meta charset = "utf-8">
  <title>Network Latency Calculation</title>
  <script>

     var firstNumber; // first string entered by user
     var secondNumber; // second string entered by user
 var thirdNumber; // third string entered by user
 var fourthNumber; // fourth string entered by user
     var number1; // first number to add
     var number2; // second number to add
 var number3; // third number to add
 var number4; // fourth number to add
     var sum; // sum of number1 and number2 and number3 and number4
 var sumresult;




     // read in first number from user as a string
     firstNumber = window.prompt( "Enter the Propagation time  (no negative number, letter, blank space, and symbol is not allow)" );

     // read in second number from user as a string
    secondNumber = window.prompt( "Enter the Transmission time  (no negative number, letter, blank space, and symbol is not allow)" );


 // read in third number from user as a string
     thirdNumber = window.prompt( "Enter the Queuing time  (no negative number, letter, blank space, and symbol is not allow)" );


 // read in fourth number from user as a string
     fourthNumber = window.prompt( "Enter the Propagation delay  (no negative number, letter, blank space, and symbol is not allow)" );








     // convert numbers from strings to integers
     number1 = parseFloat( firstNumber ); 
     number2 = parseFloat( secondNumber );
 number3 = parseFloat( thirdNumber );
 number4 = parseFloat( fourthNumber );

     sum = number1 + number2 + number3 + number4; // add the numbers

 sumresult = parseFloat( sum );


     // display the results
     document.writeln( "<h1>The network latency is " + sum + "</h1>" );
 document.writeln( "<p>Propagation time " + number1 + "</p>" );
 document.writeln( "<p>Transmission time " + number2 + "</p>" );
 document.writeln( "<p>Queuing time " + number3 + "</p>" );
 document.writeln( "<p>Propagation delay " + number4 + "</p>" );

 if ( sumresult < 1 )
        document.writeln( "<p>Network performance is good.</p>" );
 else ( document.writeln( "<p>Warning: Network performance needs improvement.</p>" ));






  </script>
</head><body></body>

Answer 1

在生产网络应用程序中，您不会提示用户输入数字 - 您将显示一个表格供用户填写。

但是，由于我们正在使用玩具应用程序，您只需重复提示，直到用户正确使用：

function getNumberFromUser(promptText) {
    var n = NaN;
    while(isNaN(n) || (n < 0)) {
       var nString = window.prompt(promptText);
       n = parseFloat(nString);
    }
    return n;
}
 var number1 = getNumberFromUser("Enter the Propagation time  (no negative number, letter, blank space, and symbol is not allow)");
 var number2 = getNumberFromUser("Enter the Transmission time  (no negative number, letter, blank space, and symbol is not allow)");
 //etc

如何使用isNaN检查输入是否为数字？

1 个答案: