JavaScript 数组。将计算值插入数组返回未定义

Question

我创建了一个表单，需要在其中输入数值，然后计算这些数值并将其填充到另一个表单中。然后，需要将计算出的输出添加到数组中，以供稍后在 session 中引用。

processOrder 函数中的所有数据都成功推送到各自的数组，但是一旦我尝试推送已计算的任何数据而不是简单地输入，则未定义的函数不会被返回。

非常感谢任何帮助。

HTML

<form>
<fieldset>
Units:<input type="number" value="" id="formUnits">   
Kms:<input type="number" value="" id="formKms">   
<input type=button value='Submit Order' onClick='calculate()'>
</fieldset>
</form>

<form>
<fieldset>
Per Unit Costs: <input type="number" id="perUnitCost">
Delivery Charges: <input type="number" id="deliveryCharge">
Pre Tax Total: <input type="number" id="preTaxTotal">
</fieldset>
</form>

JavaScript

var units = new Array();
var kms = new Array();
var timeStamp = new Array();

var unitCost = new Array();
var delivery  = new Array(); 
var preTax  = new Array();

function calculate(){           
var units = document.getElementById("formUnits").value;           
var kms = document.getElementById("formKms").value;     

if ( units >= 1 && units <= 50 ) 
{
unitCost = 11.1 * units 
} 

if ( kms >= 1 && kms <= 20 ) 
{
delivery = 20
} 

var preTax = unitCost + delivery; 
document.getElementById("perUnitCost").value = unitCost.toFixed(2);   
document.getElementById("deliveryCharge").value = delivery;  
document.getElementById("preTaxTotal").value = preTax.toFixed(2);   

processOrder()

} 

function processOrder(){

units.push(document.getElementById('formUnits').value); 
document.getElementById('formUnits').value=''; 
kms.push(document.getElementById('formKms').value); 
document.getElementById('formKms').value=''; 
timeStamp.push(Date()).value;

add_calcs_to_array()
}

function add_calcs_to_array(){

unitCost.push(document.getElementById('perUnitCost').value); 
document.getElementById('perUnitCost').value='';
delivery.push(document.getElementById('deliveryCharge').value); 
document.getElementById('deliveryCharge').value=''; 
preTax.push(document.getElementById('preTaxTotal').value); 
document.getElementById('preTaxTotal').value=''; 

}

Answer 1

我看到的问题是你的变量应该在计算中初始化为 var 以隐藏全局变量。就像这样:

// This is a global variable.
Var unitCost = [];

function calculate(units) {
  // The var unitCost here occult the global unitCost variable.
  // This means that this unitCost is local to the function.
  var unitCost = 0;
  if (units) {
    unitCost = units * 11.1;
  }
}

calculate(2);
console.log(unitCost); // Still []. Without var in calculate, it would be a 22.2.