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javascript - 我想在数组中的对象中返回一个属性，但它会导致代码中的其他问题

问题描述

所以我正在使用这个应该让汽车改变车道的功能。只要我不归还车牌，它就会变道return vehicleObject_list[i]。但是当我按照指示归还车牌时，汽车停止了变道return vehicleObject_list[i].Number_Plate。详情如下：

function moveLanes(target_car)
{
    /*
    This function should do the following: 
     - move target_car from one lane to the other.
     - do the move in a single step without any extra animation.
     - use Lane_Position_a and Lane_Position_b to effect the change.
     - finally you should return target_car at the end of the function.
     hint: You will need to modify the x property of target_car.
    */
    if(checkCarInfront(target_car).x == Lane_Position_a ){
        target_car.x = Lane_Position_b;
    }   
    else {
        target_car.x = Lane_Position_a;
    }
    
}


function checkCarInfront( carObj )
{
    /*
    This function should do the following: 
     - determine if carObj is in the same lane and less than 200px behind any of the cars in vehicleObject_list.
     - do this by traversing vehicleObject_list and comparing each car's Distance_Driven property to that of carObj.
     - if you find a car that matches these requirements then return the Number_Plate property for the car. Otherwise return false.
    */
    
    for (var i = 0; i < vehicleObject_list.length; i++)
    {
        if (carObj.x == vehicleObject_list[i].x && ((vehicleObject_list[i].Distance_Driven - carObj.Distance_Driven) < 200) && ((vehicleObject_list[i].Distance_Driven - carObj.Distance_Driven) > 0))
        {
            return vehicleObject_list[i].Number_Plate;
        }
    }
    return false;
    
    
}

var vehicleObject_list = [
{ x: 500, y: 0, Distance_Driven: -200, Car_Type: 'greenCar', Number_Plate: 'MBH0WW', Gas_Amt: 2, exhaust: [  ]} , { x: 500, y: 0, Distance_Driven: 200, Car_Type: 'whiteCar', Number_Plate: 'RLDGCM', Gas_Amt: 2, exhaust: [  ]} , { x: 300, y: 0, Distance_Driven: 600, Car_Type: 'whiteCar', Number_Plate: '9WGXXI', Gas_Amt: 2, exhaust: [  ]} ]

Detective_CarObject = 
    {
        x: roadLeftEdge + roadWidth/4,
        y: 550,
        Distance_Driven: 0,
        Gas_Amt: 3,
        EngineShudder_Value: 0,
        Car_Type: 'detective',
        Number_Plate: '5L3UTH',
        exhaust: []
    }

标签： javascriptfunctionobjectp5.js

解决方案

您可以执行以下操作：

if(checkCarInfront(target_car) && target_car.x == Lane_Position_a ){
    target_car.x = Lane_Position_b;
} else {
    target_car.x = Lane_Position_a;
}

因为checkCarInfront(target_car)如果有匹配项，将返回一个车牌字符串（它将作为非空字符串评估为真）。您可以将条件链接到target_car具有.x属性的对象。

请务必手动测试数据。（例如，如果您调用当前值vehicleObject_list和值，这将是错误的（由于）。但是，您可以暂时将'sx 设置为并在列表中添加额外的测试车以检查您的逻辑：）Detective_CarObjectcheckCarInfront(Detective_CarObject)Distance_DrivenDetective_CarObject500{ x: 500, y: 0, Distance_Driven: 199, Car_Type: 'rainbowCar', Number_Plate: 'R41NB0W', Gas_Amt: 2, exhaust: [ ]}

作为旁注，我建议遵守 JS 命名约定。这里有几个例子：W3Schools、FreeCodeCamp、Google JavaScript Style Guide。过去我会说选择一个（例如下划线/snake_case（例如target_cat）或camelCase（例如checkCarInFront）），但不能同时选择两者并保持一致，但现在似乎大多数人都坚持camelCase。这样做将使以后在团队中工作以及共享/贡献于开源库和项目变得更加容易。

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