Question

我想添加用户输入，但是出了点问题。没有错误，但没有任何反应。我要确保输入为数字，然后将两个输入加在一起。

override func setSelected(_ selected: Bool, animated: Bool) {
    let color = stripeView.backgroundColor
    super.setSelected(selected, animated: animated)

    if selected {
        stripeView.backgroundColor = color
    }
}

override func setHighlighted(_ highlighted: Bool, animated: Bool) {
    let color = stripeView.backgroundColor
    super.setHighlighted(highlighted, animated: animated)

    if highlighted {
        stripeView.backgroundColor = color
    }
}

function add() {
  
  var first = document.getElementById('first-number').value;        
  var second = document.getElementById('second-number').value;        

   
        firstMostBe = first;
        secondMostBe = second;
          var output;  
   if ((isNaN(firstMostBe)) || (isNaN(secondMostBe))){
     alert('one or both of the operands are not numbers');
   } else {
         output = firstMostBe + secondMostBe;
         return output;  
   } 
 
  var result = output; // place-holder, delete this and start over
  var output_field = document.getElementById('result');
  output_field.innerHTML = result;
}

Answer 1

您不需要dots: [ ...((previousValue[date] && previousValue[date].dots) || []), { key:currentValue._id, color: 'black' } ]的函数，也不需要使用Unary Plus return将输入转换为数字。您可以通过以下方式使代码更简洁

使用数组+和['first-number','second-number']，然后对其进行解构。
您不需要两次分配变量。

map()

function add() {
  
  var [first,second] = ['first-number','second-number'].map(x => +document.getElementById(x).value)  
  if ([first,second].some(x => isNaN(x))){
    alert('one or both of the operands are not numbers');
  } else {
    document.getElementById('result').innerHTML = first * second
  } 
}

<h2>Three-Layer Handlers Exercises</h2> <hr> <script src="./handlers-calculator.js"></script> first number: <input id='first-number' value=''></input><br> second number: <input id='second-number' value=''></input> <br> <button onclick='add()'>+</button> <button onclick='subtract()'>-</button> <button onclick='multiply()'>*</button> <button onclick='divide()'>/</button> <br> <p id='result'></p> <br><br> <hr> <hr>返回包含两个输入的两个值的数组。然后解构。等效于：

['first-number','second-number'].map(x => +document.getElementById(x).value)

Answer 2

您需要操作数的数值（带有unary plus +），如果您有NaN值，则需要提早返回。

稍后，您需要将运算结果分配给目标元素。

之间，您无需返回，因为这样可以阻止运行直到分配结果的位置。

function add() {
    var first = +document.getElementById('first-number').value,   // try to get a number
        second = +document.getElementById('second-number').value, // try to get a number
        output_field = document.getElementById('result');

    if (isNaN(first) || isNaN(second)) {
        alert('one or both of the operands are not numbers');
        return;                                                   // exit
    }

    output_field.innerHTML = first + second;
}

<h2>Three-Layer Handlers Exercises</h2>
first number: <input id='first-number' value=''><br>
second number: <input id='second-number' value=''><br>
<button onclick='add()'>+</button> 
<button onclick='subtract()'>-</button> 
<button onclick='multiply()'>*</button> 
<button onclick='divide()'>/</button> <br>
<p id='result'></p>

Answer 3

function add() {

    var first = document.getElementById('first-number').value;
    var second = document.getElementById('second-number').value;


    firstMostBe = first;
    secondMostBe = second;
    var output;
    if (isNaN(firstMostBe) || isNaN(secondMostBe)) {
        alert('one or both of the operands are not numbers');
    } else {
        output = parseInt(firstMostBe) + parseInt(secondMostBe);// By defaut it is string need to convert to number
        // no need to return form here 
    }

    var result = output; // place-holder, delete this and start over
    var output_field = document.getElementById('result');
    output_field.innerHTML = result;
}

有2个问题

您将在函数之间返回
您没有将值强制转换为Number（默认情况下为字符串）

无法获得加法结果

3 个答案: