在Javascript中公开方法的结果

Question

我有这样的方法：

// Parse a whole file
fs.readFile("klv-file.klv", (err, file) => {
    var KLVdata = KLV.parseKLVfile(file, options);
    var packets = KLVdata.packets;
    var nDropped = KLVdata.nDropped;
   
});

在一个小Node应用程序中。

如何在此对象之外获取可变数据包？

Answer 1

其实很简单。定义函数外部的变量，并在其中设置它们。如下所示：

// Define variables
var packets = null;
var nDropped = null;

// Parse a whole file
fs.readFile("klv-file.klv", (err, file) => {
    var KLVdata = KLV.parseKLVfile(file, options);
    packets = KLVdata.packets;
    nDropped = KLVdata.nDropped;
   
});

function doSomething(){
    // you can now use the variables anywhere
}

另外:确保只使用已定义的变量。

// Define variables
var packets = null;
var nDropped = null;

// Parse a whole file
fs.readFile("klv-file.klv", (err, file) => {
    var KLVdata = KLV.parseKLVfile(file, options);
    packets = KLVdata.packets;
    nDropped = KLVdata.nDropped;
    packetsReady(); // your callback function
});

function packetsReady(){
    // should only be called once the packets are ready
    processPackets(packets);
}

Answer 2

简单地把它传递给一个函数

let packets;
let nDropped;

function processKLV(KLVdata){
    packets = KLVdata.packets;
    nDropped = KLVdata.nDropped;
}

// Parse a whole file
fs.readFile("klv-file.klv", (err, file) => {
     processKLV(KLV.parseKLVfile(file, options));
});