我正在尝试将地理位置值存储在数组上,以便将纬度和经度存储为单独的变量,可以在以后的代码中访问。
这个想法是将数组与变量一起存储在变量pos
下。但是,当我控制台时,我总是得到一个undefined
值.log它。如果我安慰.log在返回之前,值实际上就在那里。
想法?
function onPositionUpdate(position)
{
var lat = position.coords.latitude;
var lng = position.coords.longitude;
var latlng = [lat,lng];
return latlng;
}
var pos = navigator.geolocation.getCurrentPosition(onPositionUpdate);
console.log(pos);
它不返回任何内容。而且它是异步的。
let pos;
function onPositionUpdate(position) {
// async action goes second (not undefined)
const lat = position.coords.latitude;
const lng = position.coords.longitude;
pos = [lat,lng];
console.log(pos);
}
navigator.geolocation.getCurrentPosition(onPositionUpdate);
// there are no value yet (undefined)
console.log(pos);
const pingPos = setInterval(() => {
if (pos) {
clearInterval(pingPos);
console.log(pos); // not undefined
}
}, 100);
你可以这样使用它
const getPosition = (cb) => {
const onPositionUpdate = (position) => {
const lat = position.coords.latitude;
const lng = position.coords.longitude;
pos = [lat,lng];
cb.apply(null, pos)
}
navigator.geolocation.getCurrentPosition(onPositionUpdate);
}
// use it anywhere
getPosition((position) => {
console.log(position);
});
或者使用 async/await 或 promise
const getPosition = () => {
return new Promise((resolve, reject) => {
const onSuccess = (position) => {
const lat = position.coords.latitude;
const lng = position.coords.longitude;
pos = [lat,lng];
resolve(pos)
}
const onError = () => {
console.log('Can't get location info');
reject();
}
navigator.geolocation.getCurrentPosition(onSuccess, onError);
})
}
// use it anywhere
getPosition().then((position) => {
console.log(position);
});