javascript 数组值的总和

Question

正在尝试创建表单以将单位数组中的值相加。无法使 Calc_totals 函数正常工作。

<script language="JavaScript" type="text/javascript">
function Calc(form) {

    var drink = new Array()
    drink [0] = form.drink0.value;
    drink [1] = form.drink1.value;
    drink [2] = form.drink2.value;

    var units = new Array()
    units [0] = 25;
    units [1] = 50;
    units [2] = 75;

    var number_units = new Array()
    form.units0.value = form.drink0.value * units[0];
    form.units1.value = form.drink1.value * units[1];
    form.units2.value = form.drink2.value * units[2]; 
    } 

function Calc_totals() {
    var answerValue = 0; 
    for(i=0; i < units.length; i++) 
    { 
    answerValue += Number(units[i]);
    } 
    form.total_units.value = answerValue;
}
</script>

我希望函数 Calc_totals 计算单位总数并输出到 form.total_units.value。

HTML:

<form name="calc_form" id="form" method="post">
   <table width="370" border="0" bgcolor="#EAEAEA">
<tr>
<th width="141"><h2>Drink Type</h2></th><th width="55"><h2>Number drank</h2></th>
<th width="84"><h2>Units</h2></th>
<th width="84"><h2>Calories</h2></th>
</tr>
   <tr class="table-text">
     <td class="right"><p class="table-text">Cider (4.5%)</p>
       <p class="table-text">1 x 568ml pint</p>
       <p class="table-text">e.g. Magners, Strongbow</p></td>
    <td width="55" valign="top">
      <p class="table-text">
     <input name="drink0" type="text" id="drink0" size="3" maxlength="2" onchange="Calc(form);" />
      </p></td>
    <td width="84" valign="top"><p class="table-text">
      <input name="units0" type="text" id="units0" size="4" maxlength="3" />
    </p></td>
    <td width="84" valign="top"><p class="table-text">
      <input name="calories0" type="text" id="calories0" size="4" maxlength="3" />
    </p></td>
    </tr>
<tr>
    <td class="right"><p class="table-text">Cider (7.5%)</p>
      <p class="table-text">1 x 500ml can</p></td>
    <td width="55" valign="top" class="table-text"><p class="table-text">
      <input name="drink1" type="text" id="drink1" size="3" maxlength="2" onchange="Calc(form);" />
    </p></td>
    <td width="84" valign="top"><p class="table-text">
      <input name="units1" type="text" id="units1" size="4" maxlength="3" />
      </span></p></td>
    <td width="84" valign="top"><p class="table-text">
      <input name="calories1" type="text" id="calories1" size="4" maxlength="3" />
      </span></p></td>
    </tr>
<tr>
    <td class="right"><p class="table-text">Beer (5%)</p>
      <p class="table-text">1 x 330ml bottle </p>
      <p class="table-text">e.g. Grolsch, Budweiser</p></td>
    <td width="55" valign="top" class="table-text"><p class="table-text">
      <input name="drink2" type="text" id="drink2" size="3" maxlength="2" onchange="Calc(form);" />
    </p></td>
    <td width="84" valign="top"><p class="table-text">
      <input name="units2" type="text" id="units2" size="4" maxlength="3" />
    </p></td>
    <td width="84" valign="top"><p class="table-text">
      <input name="calories2" type="text" id="calories2" size="4" maxlength="3" />
    </p></td>
    </tr>

<tr>
  <td><p class="table-text">&nbsp;</p></td>
  <td width="55" valign="top"><p class="table-text"></p></td>
  <td width="84" valign="top">&nbsp;</td>
  <td width="84" valign="top"><p class="table-text"></p></td>
</tr>

<tr>
  <td><p class="table-text"><strong>Totals per week= </strong></p></td>
  <td width="55" valign="top"><p class="table-text">&nbsp;</p></td>
  <td width="84" valign="top"><p class="table-text">
    <input name="total_units" type="text" id="total_units" size="4" maxlength="3" /> 
    units  </p></td>
  <td width="84" valign="top"><p class="table-text">
    <input name="total_calories" type="text" id="total" size="4" maxlength="3" />
  kcals</p></td>
</tr> 

<tr>  
<td colspan="2"><INPUT name="reset" value="Reset" TYPE="reset"> </td>
<td colspan="3"><input name="Calculate Total" type="button" id="Calculate Total" value="Calculate Total" onclick="Calc_totals();" /></td>
</tr>
</table>
</form>

我想要单位总数。 感谢您的帮助。

Answer 1

此代码的问题是 units 在 Calc_totals 中不可见。您有几个选择:

• 让它成为全局性的(糟糕的选择)
• 将其作为参数传递

或者，您可以使用 reduce 计算总和(ECMAScript 5 功能 - 在旧版浏览器中不起作用)

var sum = units.reduce(function(a, b) { return a + b });

和ES6版本

var sum = units.reduce((a, b) => a + b);