无法从Javascript中的嵌套函数返回值
嘿,伙计们,我准备了一个html5地理定位的项目来计算距离。我在Javascript中从嵌套函数返回值时遇到问题,有人能帮我吗 这是我的密码:无法从Javascript中的嵌套函数返回值,javascript,function,return-value,nested-loops,Javascript,Function,Return Value,Nested Loops,嘿,伙计们,我准备了一个html5地理定位的项目来计算距离。我在Javascript中从嵌套函数返回值时遇到问题,有人能帮我吗 这是我的密码: /* DISTANCE CALCULATOR FUNCTION */ function distanceCalc(latitudeB,longitudeB) { var result; if (navigator.geolocation) { navigator.geolocation.watchPosition(showPositi
/* DISTANCE CALCULATOR FUNCTION */
function distanceCalc(latitudeB,longitudeB) {
var result;
if (navigator.geolocation) {
navigator.geolocation.watchPosition(showPosition);
}
function showPosition(position) {
calc(position.coords.latitude,position.coords.longitude);
}
function calc(latitudeA,longitudeA) {
var lat1 = latitudeA;
var lon1 = longitude;
var lat2 = latitudeB;
var lon2 = longitudeB;
var R = 6371; // km
var dLat = (lat2-lat1)*Math.PI/180;
var dLon = (lon2-lon1)*Math.PI/180;
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1*Math.PI/180) * Math.cos(lat2*Math.PI/180) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.asin(Math.sqrt(a));
var d = R * c;
result = d.toFixed(1);
return result;
}
return result;
}
我想做一些像
var test = distanceCalc(44.35678,33.78546);
此代码不起作用,返回NAN值脚本和逻辑上有太多错误。此外,当获取地理位置坐标时,会发出一个同步呼叫。 试一试:
var DistanceCalc = function(latitudeB, longitudeB, onReadyCallback) {
this.latitudeB = latitudeB;
this.longitudeB = longitudeB;
this.callback = onReadyCallback;
//calling this.calc() here is ok...
};
DistanceCalc.prototype.calc = function()
{
var __calc = function(position) {
var lat1 = position.coords.latitude;
var lon1 = position.coords.longitude;
var lat2 = this.latitudeB;
var lon2 = this.longitudeB;
var R = 6371; // km
var dLat = (lat2-lat1)*Math.PI/180;
var dLon = (lon2-lon1)*Math.PI/180;
var a = (
Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1*Math.PI/180) *
Math.cos(lat2*Math.PI/180) *
Math.sin(dLon/2) * Math.sin(dLon/2)
);
var c = 2 * Math.asin(Math.sqrt(a));
var d = R * c;
var result = d.toFixed(1);
this.callback(result);
}.bind(this); //bind to DistanceCalc object context
if (navigator.geolocation) {
navigator.geolocation.watchPosition(__calc);
} else {
console.log("geolocation is not available");
this.callback(null);
}
};
function doSomething(result) {
console.log(">>> ", result);
}
var calculator = new DistanceCalc(44.35678, 33.78546, doSomething);
calculator.calc();
问题与返回值无关。您是否尝试过通过调试器运行它,看看会发生什么?旁注:应用正确的缩进可以让您的生活更轻松。我真的不确定您所说的是哪一段代码,但您有一些函数没有返回值,函数是异步的,和函数,这些函数期望在不调用任何参数的情况下调用参数。@billo您调用return showPosition;没有立场论证。