Imagine the Universe (9th Edition)/Imagine the Universe 9 - Disc 1.iso/pc/imagine/scripts/js_util.js

Text File | 2002-05-21 | 6KB | 269 lines

// The JavaScript Junkyard
// interesting and semi-useful JS snippets
// from scottandrew.com/junkyard/js/
// copyright 2001 scott andrew lepera

// getDistance()
// Returns the average distance between two specified points (usually for pixels)
function getDistance(x1,y1,x2,y2)
{
  var d =  Math.round(Math.sqrt(((x2-x1)*(x2-x1)) + ((y2-y1)*(y2-y1))));
    if (isNaN(d)) d = 0;
  return d;
}

// sortByProperty()
// Sort the array order based on a specific property of each array element,
//in forward or reverse order.
function _sortByProperty(property,rev)
{
  var fn = function(a,b)
  {
    if (a[property] < b[property])
    {
      return (rev)? 1:-1;
    } else if (a[property] > b[property])
    {
      return (rev)? -1:1;
    } else
    {
      return 0;
    }
  }
  this.sort(fn);
}

Array.prototype.sortByProperty = _sortByProperty;

// getAngle()
// Gives the angle of the radian described by the two specified points
function getAngle(x1,y1,x2,y2)
{
  var diffH = (x1-x2);
  var diffV = (y2-y1);
  if (diffH){
    var slope = diffV / diffH ;
    var angle = Math.atan(slope);
    var dgrs = (angle * 180) / Math.PI;
      if (diffH < 0){dgrs += 180;}
  }
  else if (diffV < 0){dgrs = 270;}
  else if (diffV > 0){dgrs = 90;}
  else {dgrs = 0;}
  if (dgrs < 0) dgrs = 360 + dgrs;
  return Math.round(dgrs);
}

// roundTo()
// Round p to nearest n
function roundTo(p,n)
{
    return (Math.round(n/p))*p;
}

// getRandomColor()
// Returns a random hex color.  Passing true for safe returns a web safe color
function getRandomColor(safe)
{
  var vals,r,n;
  if (safe)
  {
    v = "0369cf";
    n = 3;
  } else
  {
    v = "0123456789abcdef";
    n = 6;
  }
  var c = "#";
  for (var i=0;i<n;i++)
  {
    var ch = v.charAt(Math.round(Math.random() * (v.length-1)));
    c += (safe)?ch+ch:ch;
  }
  return c;
}

// addEvent and removeEvent
// cross-browser event handling for IE5+,  NS6 and Mozilla

function addEvent(elm, evType, fn, useCapture)
{
  if (elm.addEventListener){
    elm.addEventListener(evType, fn, useCapture);
    return true;
  } else if (elm.attachEvent){
    var r = elm.attachEvent("on"+evType, fn);
    return r;
  } else {
    alert("Handler could not be removed");
  }
}

function removeEvent(elm, evType, fn, useCapture)
{
  if (elm.removeEventListener){
    elm.removeEventListener(evType, fn, useCapture);
    return true;
  } else if (elm.detachEvent){
    var r = elm.detachEvent("on"+evType, fn);
    return r;
  } else {
    alert("Handler could not be removed");
  }
}

// Cookie handling functions

function saveCookie(name,value,days)
{
  if (days) {
    var d = new Date();
    d.setTime(d.getTime()+(days*24*60*60*1000));
    var ex = "; expires="+date.toGMTString();
  }
  else {
    var ex = "";
  }
  document.cookie = name+"="+value+ex+"; path=/";
}

function readCookie(name)
{
  var eq = name + "=";
  var ca = document.cookie.split(';');
  for(var i=0;i<ca.length;i++) {
    var c = ca[i];
    while (c.charAt(0)==' ') c = c.substring(1,c.length);
    if (c.indexOf(eq) == 0) return c.substring(eq.length,c.length);
  }
  return null;
}

function eraseCookie(name)
{
  saveCookie(name,"",-1);
}

// getParams

function getQueryArgs(global)
{
  var args = {};
  var loc = window.location.href;
  var q = loc.indexOf("?");
  if (q==-1) return false;
  loc = loc.substring(q+1);
  var pairs = loc.split("&");
  for (var i=0; i<pairs.length;i++){
    if (global) eval(pairs[i]);
    var keyval = pairs[i].split("=");
    args[keyval[0]] = unescape(keyval[1]);
  }
  return args;
}

/* inPoly()
Finds if a given point is within a polygon.

Based on Bob Stein's inpoly() function for C.
http://home.earthlink.net/~bobstein/inpoly/

Modified for JavaScript by Scott Andrew LePera.

Parameters:
poly: array containing x/y coordinate pairs that
  describe the vertices of the polygon. Format is
  indentical to that of HTML image maps, i.e. [x1,y1,x2,y2,...]

px: the x-coordinate of the target point.

py: the y-coordinate of the target point.

Return value:
true if the point is within the polygon, false if not.
*/

function inPoly(poly,px,py)
{
     var npoints = poly.length; // number of points in polygon
     var xnew,ynew,xold,yold,x1,y1,x2,y2,i;
     var inside=false;

     if (npoints/2 < 3) { // points don't describe a polygon
          return false;
     }
     xold=poly[npoints-2];
     yold=poly[npoints-1];

     for (i=0 ; i < npoints ; i=i+2) {
          xnew=poly[i];
          ynew=poly[i+1];
          if (xnew > xold) {
               x1=xold;
               x2=xnew;
               y1=yold;
               y2=ynew;
          }
          else {
               x1=xnew;
               x2=xold;
               y1=ynew;
               y2=yold;
          }
          if ((xnew < px) == (px <= xold) && ((py-y1)*(x2-x1) < (y2-y1)*(px-x1))) {
               inside=!inside;
          }
          xold=xnew;
          yold=ynew;
     }
     return inside;
}

// readFile
// retrieves the contents of a local file as a JS string.
// NS4 requires Java enabled.
// Works in Mozilla 0.9.5 +

function readFile(url)
{
  var req;
  if (document.all){
    req = new ActiveXObject("Microsoft.XMLHTTP");
  }
  else if (netscape){
    if (document.getElementById){
      req = new XMLHttpRequest();
    }
    else {
      req = new NS4HttpRequest();
    }
  }
  req.open("GET",url,false);
  req.send(null);
  return req.responseText;
}

function NS4HttpRequest()
{
  this.url = "";
  this.responseText = "";
}
NS4HttpRequest.prototype.open = function(method,url)
{
  this.url = url;
  this.method = method||get;
}
NS4HttpRequest.prototype.send = function()
{
  // thank you Mr. Pemberton
  if (this.url=="") return false;
  var line,buffer;
  this.responseText = "";
  buffer = new java.io.BufferedReader(new java.io.InputStreamReader(new java.net.URL(this.url).openStream()));
  while ((line = buffer.readLine())!=null) this.responseText+=line + "\n";
  if (buffer!=null) buffer.close();
  return true;
}