Difference between revisions of "Code snippets"

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Line 40: Line 40:
   return oHTML;
   return oHTML;
== GET a URL with callback function ==
Retrieves <code>url</code> using HTTP GET, then calls the function <code>cb</code> with the response text as its single argument.
function get(url, cb) {
    method: "GET",
      url: url,
      onload: function(xhr) { cb(xhr.responseText); }
Example usage:
function inform(text) {
  alert("The HTML of the page: \n" + text);
get("&#104;ttp://www.google.com", inform);
== POST data to a URL with callback function ==
Sends <code>data</code> to <code>url</code> using HTTP POST, then calls the function <code>cb</code> with the response text as its single argument.
function post(url, data, cb) {
    method: "POST",
    url: url,
    onload: function(xhr) { cb(xhr.responseText); }
Example usage:
  post('&#104;ttp://www.flash-mx.com/mm/viewscope.cfm', 'userid=joe&password=guessme', function(text) {
    alert('HTML of the page:' + text)
== better Settings Class ==
This code allows you to set and get also object values. Because of having problems with long integers, i also tranlated integers into srings
function Settingsobject(){
Settingsobject.prototype.set=function(name, value){
  if(typeof value == "boolean")
    value = value ? "{b}1" : "{b}0";
  else if(typeof value == "string")
    value = "{s}" + value;
  else if(typeof value == "number")
    value = "{n}" + value;
    value = "{o}" + value.toSource();
  GM_setValue(this.prefix+""+name, value);
  var value=GM_getValue(this.prefix+""+name, this.default[name] || "{b}0")
    return value;
      return eval("("+value.substr(3)+")");
      GM_log("Error while calling variable "+name+" while translating into an object: \n\n"+e+"\n\ncode:\n"+value.substr(3))
      return false;
    return !!parseInt(value.substr(3));
    return parseFloat(value.substr(3));
    return value.substr(3);
  return value;
Settingsobject.prototype.register=function(name, defaultvalue){
  return true;
Example usage:
var globalSettings=new Settingsobject();
The Prefix is good for seperating between accounts.
Setting variable ''x'' to 1:
globalSettings.register("x", 0);
Yo do not have to register a variable, but so you can set a default value and you have an overfiew over all variables in your Settings.default object.
== RegExp escape string ==
Escapes regexp meta characters in a string.
function escapeRegExp(s) {
  return s.replace(/([.*+?^${}()|[\]\/\\])/g, '\\$1');
Example usage:
var re = new RegExp("^" + escapeRegExp("fo*bar") + "$");
"fo*bar".match(re);  // Matches
"foobar".match(re);  // Doesn't match
== !important Style ==
Appends !important to each rule then adds the CSS to the page letting you override the site's default formatting.
  function addStyle(css) {
    GM_addStyle(css.replace(/;/g,' !important;'));
Example usage:
  addStyle('a {text-decoration:none;}');
== Make menu toggle ==
A common pattern is to [[GM_registerMenuCommand|register a menu command]] that toggles some script variable that is persisted using [[GM_getValue|GM_get]]/[[GM_setValue|setValue]]. This function abstracts that functionality.
function makeMenuToggle(key, defaultValue, toggleOn, toggleOff, prefix) {
  // Load current value into variable
  window[key] = GM_getValue(key, defaultValue);
  // Add menu toggle
  GM_registerMenuCommand((prefix ? prefix+": " : "") + (window[key] ? toggleOff : toggleOn), function() {
    GM_setValue(key, !window[key]);
The first argument is the key used with GM_get/setValue and is also the variable which will hold the current value. The second argument is the default value.
The third and fourth arguments are the text to be displayed in the menu for toggling on and toggling off, respectively. The fifth argument is an optional prefix for those menu items.
Only one menu command is added, that will toggle the option.
Example usage:
makeMenuToggle("linkify_emails", true, "Include e-mail addresses", "Exclude e-mail addresses", "Linkify");
if (linkify_emails)
'''Note''' that after changing the value, the page is reloaded so that the script runs again with the changed options, and to update the menu. This is not recommended if the user might have unsaved input on the page in question. In such a case, consider adding a <code>prompt</code> or re-running some method instead. Since menu items can't be edited/removed without reloading the page, one would likely also want two separate menu items instead of a toggle.
== Serialize/deserialize for GM_getValue ==
Used to store and retrieve multiple values (typically as a serialized hash) in a single [[GM_getValue]] slot.
function deserialize(name, def) {
  return eval(GM_getValue(name, (def || '({})')));
function serialize(name, val) {
  GM_setValue(name, uneval(val));
Example usage:
var settings = {a: 1, b: 2, c: 3};
serialize('test', settings);
var _settings = deserialize('test');
// now "settings == _settings" should be true
== make an array persistent in globalStorage ==
[http://developer.mozilla.org/en/docs/DOM:Storage DOM:Storage] is available in Firefox 2 and up.
    Makes an given Array persistent in the globalStorage Object. It will not work
    with arrays that get additional mutator functions after it was made persistent.
    @param {String} name - name of the property of this that is the Array
    @param {String} domain - domain parameter of globalStorage
    @param {Array{String, String, ...}} add_mutator - additional non standard (JavaScript 1.7) functions
  function makeArrayPersistent(_name, _domain, _add_mutator){
    //workaround for scripts that work on pages stored on file://
    var domain = _domain || ".localdomain";
    //if the array is not defined yet we define it and fill it
    //with values stored in globalStorage
      var evalStr = String(globalStorage[domain][_name]);
      this[_name] = eval(evalStr);
    //if it is defined allready we store it in globalStorage
      globalStorage[domain][_name] = uneval(this[_name]);
    //Watch will intercept asignments to this[_name] and store the new array in
    //globalStorage. The original array in globalStorage is discarded.
    this.watch(_name, function(_prop, _oldVal, _newVal){
      globalStorage[domain][_name] = uneval(_newVal);
      return _newVal;
    //see a few lines below
    ["push", "pop", "reverse", "shift",
    "sort", "splice", "unshift"].forEach(makeMutatorFunctionGlobal);
    //you can supply additional functions that will be wrapped
    //member functions that alter the array itself are wrapped. The wrapper will
    //call the mutator function and store the altered array in globalStorage
    function makeMutatorFunctionGlobal(_f){
      this[_name][_f] = function(){
        var f = this[_name][_f];
        return function(){
          var retVal;
          retVal = f.apply(this, arguments);
          globalStorage[domain].trolls = uneval(this);
          return retVal;
=== Example Usage ===
We create an array in window.
  var a = [1, 4, 3, 2];
The following would not work:
  function baz(){
    var b;
    makeArrayPersistent("b", "example.org");
We cant keep track of variables that that are not kept track of by JavaScript itself.
  makeArrayPersistent("a", "example.org");
We have to supply the variables name due to watch. <code>this["a"]</code> equals <code>this.a</code> in our case. If you want to store an object in a different scope you can use <code>makeArrayPersistent.call(some.object, "a", "example.org");</code>. The domain has to match the domain of the site where your script is injected too. Read up on <code>globalObject</code> for details.
Now a equals <code>[1, 4, 3, 2, 5]</code>. It is stored in <code>globalObject</code> that way.
And now it's <code>[1, 2, 3, 4, 5]</code>, stored again.
  delete this.a;
Now the array does not exist in this anymore. But it is kept in <code>globalObject</code>. In the next line a will be defined in this and filled from <code>globalObject</code>.
  makeArrayPersistent("a", "dexhome.homelinux.org");
And <code>this.a</code> equals <code>[1, 2, 3, 4, 5]</code> again.
If the user of your script got the same page open in two tabs the two scripts will start to fight over <code>globalStorage</code> and you will lose data. You have to alter <code>makeMutatorFunctionGlobal</code> with some meaningfull logic to counter this. The idea is to retrieve the array from <code>globalStorage</code>, combine it with the local copy and run the wrapped mutator function. Afterward it's stored in <code>globalStorage</code> again.
==Waiting for something==
Sometimes a script has to wait for some AJAX to finish before it can run this lets you do that
  function wait(c,f){
    if (c()) f()
    else window.setTimeout(function (){wait(c,f)},300,false);
Example usage:
    function(){return count==0},
== Add commas to numbers==
Numbers look more readable with commas, the following function will add them to every integer in a string.
<pre>function commafy(num) {
var str = (num+"").split("."),
return (dec) ? num+'.'+dec : num;
<pre>  commafy("123456789.12345");
  //gives: "123,456,789.12345"</pre>

== Make script accessible to Firebug ==
== Make script accessible to Firebug ==

Revision as of 10:47, 4 February 2010

Note: Contents in the process of being migrated to separate pages within Category:Coding Tips.

Hijacking browser properties

Sometimes you want to cook your own browser constants, for instance change the value of navigator.userAgent. Getters are good for that:

var real = window.navigator.userAgent;
var lie = function() { return real + " Macintosh"; };
unsafeWindow.navigator.__defineGetter__("userAgent", lie);

Extending the DOM with missing functions

Other times you might want to emulate proprietary functionality of another browser, for instance when a site uses such features:

var getter = function() { return this.textContent; };
var setter = function(t) { return this.textContent = t; };
unsafeWindow.HTMLElement.prototype.__defineGetter__("innerText", getter);
unsafeWindow.HTMLElement.prototype.__defineSetter__("innerText", setter);

Here is a function to get outerHTML without using unsafeWindow (note: the above isn't working with FF3 and GM 0.8, anyway).

function outerHTML(el){
  // create range of element
  var rng=document.createRange();
  // create temp span around element
  var tempSpan=document.createElement("span");
  // what we came for
  var oHTML=tempSpan.innerHTML;
  // remove temp span
  var frag = rng.cloneContents();
  tempSpan.parentNode.replaceChild(frag, tempSpan);
  // remove range
  // output
  return oHTML;

Make script accessible to Firebug

Firebug's console is very useful but can't access functions in a script this can make debugging them tiresome. The following code will run the entire script in the page so you can mess about with it from Firebug.

function a() {return a.caller.toString().replace(/([\s\S]*?return;){2}([\s\S]*)}/,'$2')}

Embed a function in the current page

function embedFunction(s) {


function helloWorld() { alert("hello world"); }
varBody = document.getElementsByTagName("body")[0];
varBody.innerHTML = varBody.innerHTML+ '<a title="Click me" href="javascript:helloWorld();">Click for hello world</a>';

Dump the properties of an object

This function will allow you to easily dump the properties of an object and their values to the firebug console, or anywhere else you like. I know it is long, but it also does nice formatting on the output, helping it to be readable

 /* dumpObj courtesy of Scott Van Vliet
 *  http://weblogs.asp.net/skillet/archive/2006/03/23/440940.aspx
 *  usage:
 *  params: all are optional except obj
 *  obj        -> OBJECT    your object to dump
 *  name       -> STRING    the name of your object if you want it printed
 *  maxDepth   -> NUMBER    the maximum nested objects that will be dumped. Defaults to 0, because 
 *                          it grows exponentially, so most of the time, it will be better and
 *                          easier to read if you just call dump on the child object manually.
 *  format     -> BOOLEAN   whether to format the output (default=1). Turn this of if you have to
 *                          HTML content from it, to keep the indent low.
 *  indent     ↓
 *  tabsize    ↓
 *  depth      ↓
 *  tabs       -> these are for internal communication when recursing.., if you plan on touching
 *                them, you shouldn't need documentation...lol
 *  The formatting works well only if viewed in a monospaced font. This means good in the firebug
 *  console, and probably bad in alert boxes, unless you set your chrome to use a monospace font...
 *  modifications by Naja Melan ( najamelan<AT>gmail )
 function dump( obj, name, maxDepth, format, indent, tabsize, depth, tabs ) 
   if( typeof obj      == "undefined" ) return "dumpObj: No object was passed in!\n";
   if( typeof maxDepth == "undefined" ) maxDepth = 0;
   if( typeof name     == "undefined" ) name     = "<root object>";
   if( typeof format   == "undefined" ) format   = 1;
   if( typeof indent   == "undefined" ) indent   = "";
   if( typeof tabSize  == "undefined" ) tabSize  = 8;
   if( typeof depth    == "undefined" ) depth    = 0;
   if( typeof tabs     == "undefined" ) tabs     = "";
   if( typeof obj != "object" ) return obj;
   var child = null,
       output = [];
   output.push( indent + name + "\n" );
   if( format )
     indent += "  ";
     var maxLength = 0;
     for( var item in obj )
       if( item.toString().length > maxLength ) maxLength = item.toString().length;
   for( var item in obj )
      child = obj[item];
     catch (e) 
      child = "<Unable to Evaluate>";
     if( format )
       var numSp   = maxLength - item.toString().length + 1,
           tabs    = "";
       while( --numSp > 0 ) tabs += " ";
     if( typeof child == "object" ) 
       if( depth >= maxDepth ) 
         output.push(  indent + item + tabs + ": <object, max depth reached>\n" );
           var temp = dump( child, item, maxDepth, format, indent, tabsize, depth + 1, tabs );
         catch( e )
           output.push( indent + item + tabs + ": <object could not be iterated, Error name: '" +
                        e.name + "'. Error message: '" + e.message + "'>\n" );
           temp = null;
         if( temp == indent + item + "\n" )
           output.push( indent + item + tabs + ": <object, only has built-in properties>\n" );
         else if( temp )
           output.push( " \n" );
           output.push( temp );
           output.push( "\n------------------------------------------------------------------------<end of " +
                        item + ">---------------------------------------------- \n \n" );
       if( format )
         var intro   = indent + item,
             length  = intro.length + numSp + 1,
             indent2 = "  ";
         while( --length > 0 ) indent2 += " ";
         var intro   = indent + item,
             tabs    = indent2 = "";
       output.push( intro + tabs + ": " + 
         ( ( !format )? child : child.toString().replace( /({)\n   ( \[native code\])\n(})/,
           "$1$2 $3"  ).replace( /(\r\n|[\r\n]+|<br ?\/?>)/gm, "$1" + indent2 + tabs ) ) + "\n" );
   return output.join( "" );

Force Links to Open in Another Window

Useful when you have altered the page in a custom way (i.e. via user input) and need to preserve the customized page without repainting form fields or customized nodes. This assumes only anchor links, not button or JavaScript induced links:

 var anchorTags=document.links;
 for (var i=anchorTags.length - 1; i >= 0;--i)

nextSibling function that skips whitespace

function nextSibling(startSib){
    var nextSib;
    if (!(nextSib=startSib.nextSibling)) 
        return false;
    while (nextSib.nodeType!=1) 
        if (!(nextSib=nextSib.nextSibling)) 
            return false;
    return nextSib;

Example Usage

if (nextSib=nexSibling(element))