为什么只有一个变量才能改变

Question

以下是我从主程序中删除的子例程。它是独立脚本的执行，但没有比主要程序中的预期方式更好的行为：

//Generate permanent array of all possible directional marker pairs,
//excluding 0,0. Also generate array length the "hard" way
var potential_direction_pairs = [];
var length_of_potential_direction_pairs_array = 0;
for (var x_count = -1; x_count < 2; x_count++) {
    for (var y_count= -1; y_count < 2; y_count++) {
        if (x_count == 0 && y_count == 0) {}
        else {
            potential_direction_pairs.splice(0, 0, [x_count, y_count]);
            length_of_potential_direction_pairs_array += 1
        }   
    }
}
//Create temporary and mutable copy of permanent directional marker array.
var direction_pairs_being_tried = potential_direction_pairs;
//Iterate over all elements in temporary marker array. Use permanent array
//length, as temporary array length will change with each loop.
for (var count = 0, current_direction_pair_being_tried; count < length_of_potential_direction_pairs_array; count++) {
    //Count out current length of (shrinking) temporary array.
    for (var pair_index = 0; direction_pairs_being_tried[pair_index] != undefined; pair_index++) {}
    //Choose a random marker pair from temporary array...
    var random_index = Math.floor(Math.random() * pair_index);
    //...and store it temporarily in a single-pair array.
    current_direction_pair_being_tried = direction_pairs_being_tried[random_index];
    //Remove the randomly chosen marker pair from larger temporary array.
    direction_pairs_being_tried.splice(random_index, 1);
    //Insert temporary "tracer" to display current state of intended
    //"permanent" array.
    console.log("Potential direction pairs: " + potential_direction_pairs);
    //Insert another "tracer" to display current state of intended
    //temporary array.
    console.log("Direction pairs being tried: " + direction_pairs_being_tried);
    //"Tracer" showing current state of temporary single-pair array.
    console.log("Current direction pair being tried: " + current_direction_pair_being_tried);
}

两个" 2D"阵列中只有一个要更改，但是从以下终端窗口输出的屏幕截图中， ot ot do：简单子例程的输出。我对范围/闭合/等的了解仍然很不稳定，但是我的怀疑是指向。任何帮助都将不胜感激(包括简短的解释(，但是我特别热衷于最简单的更正来进行这项工作。

事先感谢，
Rob

Answer 1

var direction_pairs_being_tried = potential_direction_pairs;不是数组的副本，它指向同一数组。您可以使用

复制数组

var direction_pairs_being_tried = potential_direction_pairs.slice()