如果为else，则活动级别为statement..calculation

Question

var bmr=100;
var sum=50;
var caloriesneeded = 0;

var activitylevel = prompt("Enter your activity level ");
document.write( "<p>You need to consume ");

if ( activitylevel == "0"){
   document.write (caloriesneeded = bmr * 1.2 );

}
else if (activitylevel == "1-3"){
   document.write(caloriesneeded = bmr *  1.375 );

}
else if (activitylevel == "3-5"){
    document.write(caloriesneeded = bmr *  1.55 );

}
else if (activitylevel == "6-7"){
    document.write (caloriesneeded = bmr * 1.725 );

}
else if (activitylevel == "2x"){
    document.write(caloriesneeded = bmr * 1.9 );

}

else {
    document.write("invalid");
}



if (caloriesneeded > sum){
    document.write ("<p>You still can consume " + (caloriesneeded - sum) + 
"kcal of food</p>");

}

else if (caloriesneeded == sum){
    document.write("<p>You have consumed just enough " + (caloriesneeded - 
sum) + "kcal of food</p>");

}

else if (caloriesneeded < sum){
    document.write ("<p>You have over consumed  " + (sum - caloriesneeded ) 
+ "kcal of food</p>");

}

只有代码的前半部分是有效的，计算所需卡路里> sum，所需卡路里== sum和所需卡路里< sum没有显示任何结果。只有当活动级别为“无效”时，代码的第二部分才会正常工作。有人发现什么错误了吗？

Answer 1

​

var bmr=100;
var sum=50;
var caloriesneeded = 0;
var activityLevels = {
    "0": 1.2,
    "1-3": 1.375,
    "3-5": 1.55,
    "6-7": 1.725,
    "2x": 1.9
};
var output = "";

function calculateCaloriesNeeded(activityLevel) {
    if ( typeof activityLevels[activityLevel] !== "undefined") {
        caloriesneeded = bmr * activityLevels[activityLevel];
        return true;
    }
    return false;
}

var currentActivityLevel = prompt("Enter your activity level ");

if (calculateCaloriesNeeded( currentActivityLevel )) {
    // input has been valid
    output += "<p>You need to consume " + caloriesneeded + "</p>";
    if (caloriesneeded > sum){
        output += "<p>You still can consume " + (caloriesneeded - sum) + "kcal of food</p>";
    } else if (caloriesneeded == sum){
        output += "<p>You have consumed just enough " + (caloriesneeded - sum) + "kcal of food</p>";
    } else if (caloriesneeded < sum){
        output += "<p>You have over consumed  " + (sum - caloriesneeded ) + "kcal of food</p>";
    }
} else {
    output += "<p>Your input is not valid. Please choose one of “0”, “1-3”, “3-5”, “6-7” or “2x”.</p>";
}

document.write( output );

​

一种更简洁的方法。

Answer 2

我很抱歉地说，你的代码充满了错误。

document.write( "<p>You need to consume ");     // missing closing tag </p>
document.write (caloriesneeded = bmr * 1.725 ); // assign and passing a parameter at the same time?

Calculate the value and then pass it to the document eg:

caloriesneeded = bmr * 1.2;
document.write ("<p>"+caloriesneeded+"</p>");

传递给提示窗口的值是数字，不需要将它们放在引号中。

if ( activitylevel == 0){

这不是范围检查：

if (activitylevel == "1-3"){

您应该执行以下操作：

if (activitylevel >= 1 && activitylevel < 3){

如上所述，用户不知道在提示窗口中输入什么。最好有一个用户可以从中选择的列表。

在这里，我举了一个简单的例子，告诉你如何才能使它成为一个更好的解决方案。

​

$("#activeSelection").change(function() {
  var bmr = 100;
  var sum = 50;
  var caloriesneeded = 0;

  var $selection = $("#activeSelection").val();

  if ($selection == 0) {
    caloriesneeded = bmr * 1.2;
    $('#calorieResponse').text(caloriesneeded);
  } else if ($selection >= 1 && $selection < 3) {
    caloriesneeded = bmr * 1.375
    $('#calorieResponse').text(caloriesneeded);
  } else if ($selection >= 3 && $selection <= 5) {
    caloriesneeded = bmr * 1.55
    $('#calorieResponse').text(caloriesneeded);
  } else if ($selection >= 6 && $selection < 7) {
    caloriesneeded = bmr * 1.725;
    $('#calorieResponse').text(caloriesneeded);
  } else if ($selection >=8 && $selection <=10) {
    caloriesneeded = bmr * 1.9
    $('#calorieResponse').text(caloriesneeded);
  }
  
  if (caloriesneeded > sum){
    $('#consume').text("You still can consume " + (caloriesneeded - sum) + "kcal of food");

}

else if (caloriesneeded == sum){
     $('#consume').text("You have consumed just enough " + (caloriesneeded - 
sum) + "kcal of food");

}

else if (caloriesneeded < sum){
    $('#consume').text("You have over consumed  " + (sum - caloriesneeded )+ "kcal of food");

}

});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<span>Hei, what is your activity level? </span>
<select id="activeSelection">
  <option>Please select</option>
  <option value="0">Couch potato</option>
  <option value="1">Not doing much</option>
  <option value="2">Lazy</option>
  <option value="3">Little active</option>
  <option value="4">Somehow active</option>
  <option value="5">Active</option>
  <option value="6">Active 2 times a week</option>
  <option value="7">Active 3 times a week</option>
  <option value="8">Active 4 times a week</option>
   <option value="9">Active 5 times a week</option>
  <option value="10">Always on the go</option>
</select>

<div>You need to consume: </div><span id="calorieResponse"></span>
<div id="consume"></div>

​