javascript - 从函数中取出信息

Question

如何从函数中获取信息？因为当我将文件启动到终端时，

console.log(latitude1 + " " + longitude1); 

返回“未定义”，而不是当我输入时

 console.log(latitude1 + " " + longitude1);

在函数中，返回经度和纬度。

var triangulate = require('wifi-triangulate')

var latitude1;
var longitude1;

triangulate(function (err, location) {
  //if (err) throw err
  var latitude = location.lat;
  var longitude = location.lng;
  latitude1 = latitude;
  longitude1 = longitude;
});
  console.log(latitude1 + " " + longitude1); 

Answer 1

triangulate 包采用回调风格编写，您可以将其转换为异步，或直接使用

回调

var triangulate = require('wifi-triangulate')

function myTriangulate(callback) {
  triangulate(function (err, location) {
    if (err) throw err;
    callback(location);
  });
}

myTriangulate(function(loc) {
  console.log(loc.latitude + " " + loc.longitude); 
});

异步

var triangulate = require('wifi-triangulate')
//use default node's promise lib
//or similar libs like bluebird

function myTriangulate() {
  return new Promise(function(resolve, reject) {
    triangulate(function (err, location) {
      if (err) return reject(err);
      resolve(location);
    });
  }); 
}

myTriangulate().then(function(loc) {
  console.log(loc.latitude + " " + loc.longitude); 
});