javascript - 在函数外访问 JavaScript 函数变量

Question

我为我的新手道歉，但我不清楚如何在函数外访问函数内的变量。我知道您需要告诉他们一些方法，但我不能 100% 确定原因和方法。

以下面的代码为例，我想在函数之外的整个代码中使用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

其实很简单，在函数外定义即可。

编辑:更新了一个示例，并在注释中解释了所做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 */