Question

我为自己的新事物而道歉，但我并不清楚如何在函数之外的函数中访问变量。我知道你需要传递一些但是我不能百分之百地确定它们的原因和方法。

以下面的代码为例，我想在函数外部的代码中使用var degree。我该怎么做？

function DegreeToMil() 
{

//Degree's to Mils: 1 Degree = 17.777778 Mils

var degree = 10;
var mils = degree * 17.777778;

return mils;

 }

Answer 1

实际上相当简单，只需在函数外定义它。

修改：更新了示例，并说明了解已完成的工作及其工作原理。

    DegreesToMils.degrees = 10; /* This is a static variable declaration to make sure it isn't undefined
                             * See note 1 below */

function DegreesToMils(degrees) {
    if (degrees !== undefined) {
        DegreesToMils.degrees = degrees; /* If the parameter is defined, 
                                          * it will update the static variable */
    }

    var milsPerDegree = 17.777778; /* This is a variable created and accessible within the function */

    return DegreesToMils.degrees * milsPerDegree; /* The function will return 177.77778 */
}

console.log(DegreesToMils.degrees); /* Prints 10, Note 1: This would be undefined if
                                     * not declared before the first call to DegreesToMils() with a 
                                     * defined parameter
                                     */
console.log(DegreesToMils(10)); /* Prints 177.77778 */
console.log(DegreesToMils(9)); /* Prints 160.00000200000002, Sets DegreesToMils.degrees to 9 */
console.log(DegreesToMils.degrees); /* Prints 9 */

Answer 2

function DegreeToMil() 
{

    //Degree's to Mils: 1 Degree = 17.777778 Mils

    var degree = 10;
    var mils = degree * 17.777778;
    var result = [degree, mils]; // it's an array
    return result;
}

// use it like this

var myResult = DegreeToMil();
console.log(myResult[0]); // degree
console.log(myResult[1]); // mils

访问函数外部的JavaScript函数变量

2 个答案: