Question

可变时间似乎是不确定的，但是作为js的新手，他无法理解问题所在。试图全局声明var time，然后在内部条件下递增，但不起作用。

var j1 = 0;
var j2 = 0;
var j3 = 4;

var time;

if((j1||j2||j3)>=3){
    
    
   time+5000;

    while(time === 30000){
        if(j1>=3){
            alert("Junction 1 is flooded");
        }else if(j2>=3){
            alert("Junction 2 is flooded");
        }else if(j3>=3){
            alert("Junction 3 is flooded");
        }else if ((j1&&j2)>=3){
            alert("Junction 1 & 2 are flooded");
        }else if ((j1&&j3)>=3){
            alert("Junction 1 & 3 are flooded");
        }else if ((j2&&j3)>=3){
            alert("Junction 2 & 3 are flooded");
        }else if ((j1&&j3)>=3){
            alert("Junction 1 & 3 are flooded");
        }else if ((j1&&j3&&j2)>=3){
            alert("All 3 junctions are flooded");
        }
    }
}

Answer 1

time+5000;不会为您做任何事情，因为time是undefined，因为您所做的全部是声明的，但未使用以下方法初始化它：

var time; // Declared but not initialized === undefined

，并且您无法使用undefined进行数学运算。

此外，您没有捕获数学运算的结果。

设置：

var time = 0; // Declared and initialized ;)

然后：

time = time + 5000; // Assign result of expression back to variable

下一步，您的if条件不正确。必须分别进行多个值的测试，因此：

if((j1||j2||j3)>=3){

需要成为这个：

if(j1 >= 3 || j2 >= 3 || j3 >=3){

最后，现在您的代码time只会被增加一次，达到5000的值，因此您永远不会进入while循环。这样，即使进入循环，也不会在其中修改time的值，因此循环永远不会结束。您需要设置某种条件来检查以确定循环是否应该继续。应该是这样的：

while(time < 50000){
  if(time === 30000){
    if(j1 >= 3){
        alert("Junction 1 is flooded");
    }else if(j2 >= 3){
        alert("Junction 2 is flooded");
    }else if(j3 >= 3){
        alert("Junction 3 is flooded");
    }else if (j1 >= 3 && j2 >=3){
        alert("Junction 1 & 2 are flooded");
    }else if (j1 >= 3 && j3 >= 3){
        alert("Junction 1 & 3 are flooded");
    }else if (j2 >= 3 && j3 >=3){
        alert("Junction 2 & 3 are flooded");
    }else if (j1 >= 3 && j3>=3){
        alert("Junction 1 & 3 are flooded");
    }else if (j1 >=3 && j3 >=3 &&j2 >=3){
        alert("All 3 junctions are flooded");
    }
  }

  time = time + 5000;  // <-- You need to create a situation where the loop can end! 
}

因此，将它们放在一起：

var j1 = 0;
var j2 = 0;
var j3 = 4;

var time = 0;

if(j1 >= 3 || j2 >= 3 || j3 >=3){

  while(time < 50000){
      // Check what time is with an "if"
      if(time === 30000){
        if(j1 >= 3){
            alert("Junction 1 is flooded");
        }else if(j2 >= 3){
            alert("Junction 2 is flooded");
        }else if(j3 >= 3){
            alert("Junction 3 is flooded");
        }else if (j1 >= 3 && j2 >=3){
            alert("Junction 1 & 2 are flooded");
        }else if (j1 >= 3 && j3 >= 3){
            alert("Junction 1 & 3 are flooded");
        }else if (j2 >= 3 && j3 >=3){
            alert("Junction 2 & 3 are flooded");
        }else if (j1 >= 3 && j3>=3){
            alert("Junction 1 & 3 are flooded");
        }else if (j1 >=3 && j3 >=3 &&j2 >=3){
            alert("All 3 junctions are flooded");
        }
      }

      time = time + 5000;  // <-- You need to create a situation where the loop can end! 
    }
}

Answer 2

使用time+=5000;代替time+5000;

Answer 3

您应该将时间设置为0，然后使用+ =递增时间。

var time=0;

if(j1>=3||j2>=3||j3>=3){


   time+=5000;

仅编写var time;与var time = undefined相同，并且您不能对未定义的对象执行数学运算。您需要初始化变量。

要增加时间变量，您需要将其设置为5000加自身或time = time + 5000或简写time += 5000。

ReferenceError：时间未定义

3 个答案: