JavaScript：计算器使用变量

Question

我有一个问题，我无法让我的JavaScript计算器工作。当在浏览器中显示时，该部分将显示实际的代码行而不是返回的答案。这是我迄今为止所拥有的。计算在函数b()中，并打印在底部的document.write()中。

---

的JavaScript：

//*Note that this is an external JavaScript file* 
function a(a1,a2,a3) { 
    this.a1 = a1; 
    this.a2 = a2; 
    this.a3 = a3; 
    this.a4 = b; 
} 

var abc = new a("2", "80", "1000"); 
var def = new a("1.5", "40", "512"); 
var ghi = new a("1", "20", "256"); 

//Below is the calulation function I'm having problems with 
function b() { 
    var calculation; 
    calculation = 500; 
    calculation+=(this.a1 = 2) ? 200 : 100; 
    calculation+=(this.a2 = 80) ? 50 : 25; 
    calculation+=(this.a3 = 1000) ? 150 : 75; 
    return calculation; 
} 

var returned_value_abc = abc.a4(); 
var returned_value_def = def.a4(); 
var returned_value_ghi = ghi.a4(); 

document.write("Abc object: "); 
document.write("<br/>"); 
//Below is code to print out returned calculation value 
document.write("Value: "+abc.a4); 
document.write("<br/>"); 
document.write("<br/>"); 
document.write("Def object: "); 
document.write("<br/>"); 
//Below is code to print out returned calculation value 
document.write("Value: "+def.a4); 
document.write("<br/>"); 
document.write("<br/>"); 
document.write("Ghi object: "); 
document.write("<br/>"); 
//Below is code to print out returned calculation value 
document.write("Value: "+ghi.a4); 

Answer 1

你的问题很可能是这些行：

calculation+=(this.a1 = 2) ? 200 : 100; 
calculation+=(this.a2 = 80) ? 50 : 25; 
calculation+=(this.a3 = 1000) ? 150 : 75; 

在括号中的=是assignment，而不是equality comparison。使用

calculation += (this.a1 == 2) ? 200 : 100; 
calculation += (this.a2 == 80) ? 50 : 25; 
calculation += (this.a3 == 1000) ? 150 : 75;