javascript - 根据键码更改数组

Question

我尝试使用下面的代码使 arrayGroup 包含与向上或向下击键相关的数据集。根据这一点，它将从名为 numberArray1 的变量中加或减 1，并允许根据 arrayGroup 设置为哪个数据集来调用不同的数组。目前，我可以将数组作为字符串调用，但在将它们作为数组调用并将它们传递到 arrayGroup 时遇到问题。

您的建议将不胜感激!

var arrayGroup = [];

var numberArray1 = [1,2,3,4,5,6,7,8,9,10];

var numberArray2 = [10,11,12,13,14,15,16,17,18,19];

x=0;
alert(x);
document.addEventListener('keydown', function (evt) {
    if (evt.keyCode === 38) {
        alert('The "UP" key is being held down...?');
        alert(numberArray1);
        x=x+1;
        alert(x); 
        alert ("numberArray"+(x));
        arrayGroup = "numberArray"+(x);
        alert(arrayGroup);


    }
    if (evt.keyCode === 40) {
        alert('The "DOWN" key is being held down...?');
        arrayGroup = "numberArray"+(x-1);
        x=x-1;
        if(x<0){
            x=0;
            arrayGroup = "numberArray0";
        }

        alert(x);
        alert(arrayGroup);
    }
});

更新!!! - 我仍然遇到这个问题...

你好，

下面代码的目的是使用相对于从 numberArrays 获取的数据的 RGB 值来更新 SVG map 。每次用户使用光标时，我都想循环浏览不同的数组，这反过来又允许 map 改变颜色。目前我在使用全局变量 arrayGroup 时遇到困难，我无法使其余代码在按键时解释更新的数组。

如果您能提供任何建议，我们将不胜感激。

非常感谢!!!

var rsr = Raphael('map', '595.28', '841.89');

counties = [];

//obviously, this is the array storing the numbers of students for this particular year
numberArray0 =     [46,54,38,125]:    
//this empty array will store the different number categories i.e. 0-50, 51-100...
categories = [];

var arrayGroup = [];

numberArray1 = [460,200,384,135]:  

numberArray2 = [260,100,584,335]:

x=0;

if(x===0){
    arrayGroup = numberArray0;
    alert(arrayGroup);}

document.addEventListener('keydown', function (evt) {
if (evt.keyCode === 38) {
    alert('The "UP" key is being held down...?');
    x+=1;
    arrayGroup = eval ("numberArray"+(x));
    alert(arrayGroup);


}
if (evt.keyCode === 40) {
    alert('The "DOWN" key is being held down...?');
    arrayGroup = eval ("numberArray"+(x-1));
    x-=1;
    alert(arrayGroup);
        if(arrayGroup===numberArray+(-1)){
        x=0;
        alert(numberArray0);}
}
});

//this for loop populates the "categories" array with these categories, going up in       fifties (i=0; i<61 becuase 60*50=3000, the number we were taking as the highest
for(i=0; i<61; i++){
if(i==0){
categories[0]=0;   
}
else{
categories.push(categories[i-1]+50);
}
};

//empty array that will store the strings that define the colour of the counties
colourStrings=[];

//this loop goes through the population numbers for the county and finds out what category    they are.
for(var i=0; i<arrayGroup.length; i++){
for(var j=0; j<categories.length; j++){
// this is a loop within a loop. First it takes a population number and runs through all     the categories to see which one it's in
if(arrayGroup[i]>categories[j]){
//if it's bigger than the start point of the category(e.g. 71 is bigger than 50, goes in      the 51-100 bracket) we take the index 
index=j;
}


}
//the higher the category the population is in, the higher the index will be and the more     the g and b values will be reduced
//the colour value wll then be stored in colourStrings at an index that corresponds with     the county
colourStrings.push("rgb(255,"+(250-4*index).toString()+","+ (250-4*index).toString()     +")");
}

Answer 1

您正在为变量 arrayGroup 分配一个字符串值，这就是您能够将它们作为字符串访问的原因。如果您想将它们作为数组访问，只需将所需的数组分配给 arrayGroup 变量，如下所示:

arrayGroup = numberArray1;
console.log(arrayGroup);  // outputs: [1,2,3,4,5,6,7,8,9,10]

这样，arrayGroup[0]将输出1。您目前的做法是:

arrayGroup = "numberArray1";
console.log(arrayGroup[0]); // outputs: "n" because "n" is at index 0 of the string assigned to arrayGroup.

另外，关于增加和减少 x 值的一些建议:

x++; // increases the value of x by one
x += 1;  // is the same as x = x + 1
x--; // decreases the value of x by one
x -= 1; // is the same as x = x -1

我认为这回答了你的问题(尽我所能理解)。如果这不是您想要的，请告诉我，我会看看是否可以提供进一步的帮助。我希望这有帮助!