为什么这两个变量都应该改变，而只有一个应该改变？

Question

以下是我从我的主程序中删除的一个子程序。它作为一个独立的脚本执行，但并不比在主程序中表现得更好：

//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”数组中只有一个要更改，但正如您从以下终端 window 输出的屏幕截图中看到的那样，both 会： output of simple subroutine。我对 scope/closure/etc 的了解仍然很不稳定，但我怀疑是那个方向。任何帮助将不胜感激（包括简短的解释），但我特别热衷于尽可能简单的更正来完成这项工作。

提前致谢，
罗布

Answer 1

var direction_pairs_being_tried = potential_direction_pairs; 不是数组的副本，它指向同一个数组。您可以使用

复制数组

var direction_pairs_being_tried = potential_direction_pairs.slice()

为什么这两个变量都应该改变，而只有一个应该改变？

Why do both of these variables change when only one is supposed to?

javascript

scope

loops

dynamic-arrays