Inclusiones dinámicas de scripts en JavaScript

Verifica si ya se incluyó un script (en la sección de cabecera por defecto):

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//------------------------------------------------------------------------------------------------ // Engines      JavaScript 1.2+ //              JScript    3+ // Environments NN6+ IE5+ MOZILLA1+ SAFARI1+ // DOM Level    1 Core //------------------------------------------------------------------------------------------------ function included (s /* scr */, t /* tag-name (head by default) */) {     var d;     if (!t) t = 'head';       if (typeof s == 'string' && (d = s.indexOf('../')) != -1)         s = s.substr(d + 3);       d = document;     t = d.getElementsByTagName(t);       for (var i = 0, l = t.length, e; i < l; ++i)     {         e = t[i].getElementsByTagName('script');           for (var j = 0, n = e.length; j < n; ++j)             if (e[j].src && (s.test ? s.test(e[j].src) : e[j].src.lastIndexOf(s) != -1))                 return true;     }       return false; }

Uso:

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if (!included('my-file.js')) {     // TODO... }

Incluye uno o varios scripts (en la sección de cabecera por defecto):

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//------------------------------------------------------------------------------------------------ // Engines      JavaScript 1.2+ //              JScript    3+ // Environments NN6+ IE5+ MOZILLA1+ SAFARI1+ // DOM Level    1 Core //------------------------------------------------------------------------------------------------ function include (/* arg1 [, ... [, argN]] */) {     var r = '', x = r;     for (var d = document, i = 0, a = arguments, l = a.length, e, s; i < l; ++i)     {         if ((s = a[i]).root && (r = s.root + '').length > 0 && r.lastIndexOf('/') != r.length - 1)             r += '/';              if (s.extension && (x = s.extension + '').length > 0 && x.indexOf('.') != 0)             x = '.' + x;           if (s.src || typeof s == 'string')         {             e = d.createElement('script');             e.setAttribute('src',  r + (s.src ? s.src : s) + x);             e.setAttribute('type', s.type ? s.type : 'text/javascript');               if (typeof s.onload == 'function')             {                 if (e.readyState)                 {                     e.onreadystatechange = function ()                     {                         if (this.readyState == 'loaded' || this.readyState == 'complete')                         {                             delete this.onreadystatechange;                             this.loaded();                         }                     }                       e.loaded = s.onload;                 }                       else e.onload = s.onload;             }               d.getElementsByTagName(s.tag ? s.tag : 'head')[0].appendChild(e);         }     } }

Uso:

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if (!included('my-file1.js') && !included('my-file2.js')) include (       {root: 'my-path', extension: 'js'}     , {src: 'my-file1', onload: function () { /* TODO... */ }}     , {src: 'my-file2', onload: function () { /* TODO... */ }} );   if (!included('my-file4.js'))     include({src: 'my-file4.js', onload: function () { /* TODO... */ }});

Existe otro modo de hacerlo, usando ajax:

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//------------------------------------------------------------------------------------------------ // Engines      JavaScript 1.2+ //              JScript    3+ // Environments NN7.1+ IE5+ MOZILLA1+ SAFARI1.2+ //------------------------------------------------------------------------------------------------ function loadscript (s /* url */, b /* eval? (Boolean) */) {     var r, x, w = window;        if (w && w.XMLHttpRequest)         r = new w.XMLHttpRequest();        else if (typeof Components != 'undefined' && Components.classes)                               // XPCOM!     {         try         {             r = Components.classes['@mozilla.org/xmlextras/xmlhttprequest;1'].createInstance             (                 Components.interfaces.nsIXMLHttpRequest             );         }              catch (e)         {             r = null;         }     }        else if ((x = w.ActiveXObject) || (x = w.GeckoActiveXObject))     {         try         {             r = new x('Msxml2.XMLHTTP');         }             catch (e)         {             try             {                 r = new x('Microsoft.XMLHTTP');             }               catch(e)             {                 r = null;             }         }     }        if (r)     {         r.open('GET', s, false);         r.send(null);             if (r.readyState == 4 && r.status == 200)         {             if (b) eval(r.responseText);             else             {                 (w = (x = document).createElement('script')).setAttribute('type', 'text/javascript');                 w.text = r.responseText;                 x.getElementsByTagName('head')[0].appendChild(w);             }               return true;         }     }           return false; }

Uso:

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if (loadscript('my-file1.js')) {     //TODO... }   loadscript('my-file2.js', true);