Javascript執行問題

Question

此代碼計算大圓距離。原始來源是：http://www.movable-type.co.uk/scripts/latlong-vincenty.html

我確定它的東西很簡單，即丟失，但JavaScript不會執行。

http://jsfiddle.net/RvdJH/

<script type="text/javascript"> 

function distVincenty(lat1, lon1, lat2, lon2) { 
    var a = 6378137, 
     b = 6356752.314245, 
     f = 1/298.257223563; // WGS-84 ellipsoid params 
    var L = toRad(long2 -lon1); 
    function toRad(degrees){ 
     return degrees * Math.PI/180; 
    } 
    var U1 = Math.atan((1 - f) * Math.tan(lat1.toRad())); 
    var U2 = Math.atan((1 - f) * Math.tan(lat2.toRad())); 
    var sinU1 = Math.sin(U1), 
     cosU1 = Math.cos(U1); 
    var sinU2 = Math.sin(U2), 
     cosU2 = Math.cos(U2); 

    var lambda = L, 
     lambdaP, iterLimit = 100; 
    do { 
     var sinLambda = Math.sin(lambda), 
      cosLambda = Math.cos(lambda); 
     var sinSigma = Math.sqrt((cosU2 * sinLambda) * (cosU2 * sinLambda) + (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda) * (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda)); 
     if (sinSigma == 0) return 0; // co-incident points 
     var cosSigma = sinU1 * sinU2 + cosU1 * cosU2 * cosLambda; 
     var sigma = Math.atan2(sinSigma, cosSigma); 
     var sinAlpha = cosU1 * cosU2 * sinLambda/sinSigma; 
     var cosSqAlpha = 1 - sinAlpha * sinAlpha; 
     var cos2SigmaM = cosSigma - 2 * sinU1 * sinU2/cosSqAlpha; 
     if (isNaN(cos2SigmaM)) cos2SigmaM = 0; // equatorial line: cosSqAlpha=0 (§6) 
     var C = f/16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha)); 
     lambdaP = lambda; 
     lambda = L + (1 - C) * f * sinAlpha * (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM))); 
    } while (Math.abs(lambda - lambdaP) > 1e-12 && --iterLimit > 0); 

    if (iterLimit == 0) return NaN // formula failed to converge 
    var uSq = cosSqAlpha * (a * a - b * b)/(b * b); 
    var A = 1 + uSq/16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq))); 
    var B = uSq/1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq))); 
    var deltaSigma = B * sinSigma * (cos2SigmaM + B/4 * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM) - B/6 * cos2SigmaM * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM))); 
    var s = b * A * (sigma - deltaSigma); 

    s = s.toFixed(3); // round to 1mm precision 
    return s; 

    // note: to return initial/final bearings in addition to distance, use something like: 
    var fwdAz = Math.atan2(cosU2 * sinLambda, cosU1 * sinU2 - sinU1 * cosU2 * cosLambda); 
    var revAz = Math.atan2(cosU1 * sinLambda, -sinU1 * cosU2 + cosU1 * sinU2 * cosLambda); 
    return { 
     distance: s, 
     initialBearing: fwdAz.toDeg(), 
     finalBearing: revAz.toDeg() 
    }; 
}​ 

</script> 


<table> 
    <tr> 
     <td> 
      <p> 
       Lat 1: <input name="lat1" value="53.0902"> 
       Long 1: <input name="lon1" value="001.5040"> 
      </p> 
      <p> 
       Lat 2: <input name="lat2" value="52.1219"> 
       Long 2: <input name="lon2" value="040.0833"> 
      </p> 
      <input type="button" value="calculate distance" onClick="document.getElementsByName('result')[0].value = distVincenty(document.getElementsByName('lat1')[0].value ,document.getElementsByName('lon1')[0].value , document.getElementsByName('lat2')[0].value, document.getElementsByName('lon2')[0].value);"> 
     </td> 
    </tr> 
</table> 


</body> 

Answer 1

你不能訪問諸如result.value輸入值。使用像

document.getElementsByName('result')[0].value 

而代碼獲取toRad未定義的錯誤。添加此方法

Number.prototype.toRad = function() { // convert degrees to radians 
return this * Math.PI/180; 
} 
Number.prototype.toDeg = function() { // convert radians to degrees 
    return this * 180/Math.PI; 
}