Javascript变量未正确添加两个变量，仅进行级联 [英] Javascript variables not adding two variables correctly, only concatenating

问题描述

我正在使用html/javascript创建座位预订页面.

I am creating an seat booking page with html/javascript.

这是我正在研究的标准的一部分:

This is part of the criteria I am working on:

• 当1至4位乘客时，每英里车费增加£0.10

• When Passengers 1 to 4, Add £0.10 to Fare per mile

当里程数小于或等于10时，则每英里票价为£1.-

When number of miles is less than or equal to 10, then Fare per mile is £1.-

问题是，当我尝试将乘客的总费用+费用相加时，它将变量连接在一起(两种方法都尝试过).

The problem is, is that when I try to add together the total cost + cost for passengers, it concatenates the variable (tried it both ways).

任何帮助将不胜感激.

function MyFunction() {
  var x, text, passengers, passengerresponse, cost;

  miles = document.getElementById("miles").value;
  
  if (isNaN(miles) || miles < 1) {
    text = "Input not valid";
  } else if (miles <= 10) {
    cost = miles;
  }
  
  document.getElementById("miles2").innerHTML = miles;

  passengers = document.getElementById("passengers").value;

  if (passengers >= 1 && passengers <= 4) {
    passengerresponse = "OK";
    cost += passengers / 10;
  }
  document.getElementById("passengers2").innerHTML = passengers;
  document.getElementById("totalcost").innerHTML = cost;
}

Journey in miles:
<input id="miles" type="number">
<p id="miles2"></p>

Number of passengers:
<input id="passengers" type="number">
<p id="passengers2"></p>

<button type="button" onclick="MyFunction()">Submit</button>

Total cost:
<p id="totalcost"></p>

推荐答案

passengers是字符串，而不是数字.您所做的与说出cost ='Santa'+'Claus'相同；它的成本='1'+'4';不会将"1"和"4"更改为1和4.

passengers is a string, not a number. You're doing the same thing as saying cost = 'Santa' + 'Claus'; The fact that it's cost = '1' + '4'; doesn't change the '1' and '4' to a 1 and 4.

解决方案是使用 parseInt ，数字或其中之一此答案中的方法.

The solution is to use parseInt, Number, or one of the method from this answer.

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