Question

我正在通过javascript函数计算给定点的行和列。
要实现这一点，我必须声明全局变量

var global_row;
var global_col;

这是功能正文

function calculate_city_row_col(cur_city_id)
{
    var r = 565;
    var c = 1;
    var max_city_id = 159895;
    do{
        if((r%2) == 0) c++;
        max_city_id -= r;
        r--;
    }
    while(cur_city_id <= max_city_id)

    //Saving Result in seperate row and column
    global_row = r + 1;                                 //Global Variable
    global_col = c + (cur_city_id - (max_city_id + 1)); //Global Variable
}

这是函数调用

var city_id = 1244;
calculate_city_row_col(city_id);
var city_row = global_row;
var city_col = global_col;

无论如何直接传递局部变量？（不使用全局变量）
像这样

calculate_city_row_col(cur_city_id, city_row_ref, city_col_ref);

Answer 1

只需返回一个对象：

function calculate_city_row_col(cur_city_id)
{
    var r = 565;
    var c = 1;
    var max_city_id = 159895;
    do{
        if((r%2) == 0) c++;
        max_city_id -= r;
        r--;
    }
    while(cur_city_id <= max_city_id)

    return {
        row: r + 1,
        col: c + (cur_city_id - (max_city_id + 1))
    };
}

var rowAndCol = calculate_city_row_col(1244);
var city_row = rowAndCol.row;
var city_col = rowAndCol.col;

Answer 2

我们可以通过JavaScript函数
中的引用传递变量

没有。 JavaScript纯粹是按值传递（传递对象时传递的值是对象引用，但它仍然是值）。

您的选择是：

让函数返回一个对象（或数组）

function calculate_city_row_col(cur_city_id)
{
    var r = 565;
    var c = 1;
    var max_city_id = 159895;
    do{
        if((r%2) == 0) c++;
        max_city_id -= r;
        r--;
    }
    while(cur_city_id <= max_city_id)

    //Saving Result in seperate row and column
    return {
        row: r + 1,
        col: c + (cur_city_id - (max_city_id + 1))
    };
}

用法：

var result = calculate_city_row_col(someCityId);
console.log(result.row);
console.log(result.col);

让函数接受对它更新的对象（或数组）的引用

function calculate_city_row_col(cur_city_id, result)
{
    var r = 565;
    var c = 1;
    var max_city_id = 159895;
    do{
        if((r%2) == 0) c++;
        max_city_id -= r;
        r--;
    }
    while(cur_city_id <= max_city_id)

    //Saving Result in seperate row and column
    result.row = r + 1;
    result.col = c + (cur_city_id - (max_city_id + 1));
}

用法：

var result = {};
calculate_city_row_col(someCityId);
console.log(result.row);
console.log(result.col);

除非在特定情况下选择＃2，否则＃1通常是最佳选择。例如，如果您在紧密循环中调用此函数数千次，则可能是重用单个对象（通过传入）而不是每次都创建新对象的理由。 / p>

我们可以在JavaScript函数中通过引用传递变量吗？

2 个答案: