Carica dynamicmente il file javascript esterno e attendi che venga caricato, senza usare JQuery

Sto provando a caricare dynamicmente un file .js esterno (in base a un input che ottengo dall’utente). Attualmente il mio codice assomiglia a questo:

function createScript(src, id) { if (document.getElementById(id) == null) { var newScript = document.createElement('script'); newScript.setAttribute("type", "text/javascript"); newScript.setAttribute("src", src); newScript.setAttribute("id", id); document.getElementsByTagName("head")[0].appendChild(newScript); } } 

Questo tipo di lavoro. Carica lo script, ma se provo a chiamare una funzione definita all’interno del nuovo script, non funzionerà. La cosa strana è che se aspetto un secondo (usando un alert("test") o qualcosa del genere) lo script funziona.

Immagino sia perché il browser aggiunge immediatamente il tag , ma ci vuole un po ‘più tempo per “leggere” lo script all’interno del file .js. Ho provato a giocare con "typeof testfunction === 'function'" con alcune varianti ma senza fortuna.

Qualche buon modo per farlo?

21 febbraio 2017: come fa jQuery

jQuery.getScript ora è solo un wrapper per jQuery.get

 getScript: function( url, callback ) { return jQuery.get( url, undefined, callback, "script" ); } 

jQuery.get è solo un wrapper di jQuery.ajax – è definito usando metaprogrammazione come …

 jQuery.each( [ "get" , "post" ], function( i, method ) { jQuery[ method ] = function( url, data, callback, type ) { // Shift arguments if data argument was omitted if ( jQuery.isFunction( data ) ) { type = type || callback; callback = data; data = undefined; } // The url can be an options object (which then must have .url) return jQuery.ajax( jQuery.extend( { url: url, type: method, dataType: type, data: data, success: callback }, jQuery.isPlainObject( url ) && url ) ); }; } ); 

jQuery.ajax è questo mostro di 430+ LOC

 ajax: function( url, options ) { // If url is an object, simulate pre-1.5 signature if ( typeof url === "object" ) { options = url; url = undefined; } // Force options to be an object options = options || {}; var transport, // URL without anti-cache param cacheURL, // Response headers responseHeadersString, responseHeaders, // timeout handle timeoutTimer, // Url cleanup var urlAnchor, // Request state (becomes false upon send and true upon completion) completed, // To know if global events are to be dispatched fireGlobals, // Loop variable i, // uncached part of the url uncached, // Create the final options object s = jQuery.ajaxSetup( {}, options ), // Callbacks context callbackContext = s.context || s, // Context for global events is callbackContext if it is a DOM node or jQuery collection globalEventContext = s.context && ( callbackContext.nodeType || callbackContext.jquery ) ? jQuery( callbackContext ) : jQuery.event, // Deferreds deferred = jQuery.Deferred(), completeDeferred = jQuery.Callbacks( "once memory" ), // Status-dependent callbacks statusCode = s.statusCode || {}, // Headers (they are sent all at once) requestHeaders = {}, requestHeadersNames = {}, // Default abort message strAbort = "canceled", // Fake xhr jqXHR = { readyState: 0, // Builds headers hashtable if needed getResponseHeader: function( key ) { var match; if ( completed ) { if ( !responseHeaders ) { responseHeaders = {}; while ( ( match = rheaders.exec( responseHeadersString ) ) ) { responseHeaders[ match[ 1 ].toLowerCase() ] = match[ 2 ]; } } match = responseHeaders[ key.toLowerCase() ]; } return match == null ? null : match; }, // Raw string getAllResponseHeaders: function() { return completed ? responseHeadersString : null; }, // Caches the header setRequestHeader: function( name, value ) { if ( completed == null ) { name = requestHeadersNames[ name.toLowerCase() ] = requestHeadersNames[ name.toLowerCase() ] || name; requestHeaders[ name ] = value; } return this; }, // Overrides response content-type header overrideMimeType: function( type ) { if ( completed == null ) { s.mimeType = type; } return this; }, // Status-dependent callbacks statusCode: function( map ) { var code; if ( map ) { if ( completed ) { // Execute the appropriate callbacks jqXHR.always( map[ jqXHR.status ] ); } else { // Lazy-add the new callbacks in a way that preserves old ones for ( code in map ) { statusCode[ code ] = [ statusCode[ code ], map[ code ] ]; } } } return this; }, // Cancel the request abort: function( statusText ) { var finalText = statusText || strAbort; if ( transport ) { transport.abort( finalText ); } done( 0, finalText ); return this; } }; // Attach deferreds deferred.promise( jqXHR ); // Add protocol if not provided (prefilters might expect it) // Handle falsy url in the settings object (#10093: consistency with old signature) // We also use the url parameter if available s.url = ( ( url || s.url || location.href ) + "" ) .replace( rprotocol, location.protocol + "//" ); // Alias method option to type as per ticket #12004 s.type = options.method || options.type || s.method || s.type; // Extract dataTypes list s.dataTypes = ( s.dataType || "*" ).toLowerCase().match( rnothtmlwhite ) || [ "" ]; // A cross-domain request is in order when the origin doesn't match the current origin. if ( s.crossDomain == null ) { urlAnchor = document.createElement( "a" ); // Support: IE <=8 - 11, Edge 12 - 13 // IE throws exception on accessing the href property if url is malformed, // eg http://example.com:80x/ try { urlAnchor.href = s.url; // Support: IE <=8 - 11 only // Anchor's host property isn't correctly set when s.url is relative urlAnchor.href = urlAnchor.href; s.crossDomain = originAnchor.protocol + "//" + originAnchor.host !== urlAnchor.protocol + "//" + urlAnchor.host; } catch ( e ) { // If there is an error parsing the URL, assume it is crossDomain, // it can be rejected by the transport if it is invalid s.crossDomain = true; } } // Convert data if not already a string if ( s.data && s.processData && typeof s.data !== "string" ) { s.data = jQuery.param( s.data, s.traditional ); } // Apply prefilters inspectPrefiltersOrTransports( prefilters, s, options, jqXHR ); // If request was aborted inside a prefilter, stop there if ( completed ) { return jqXHR; } // We can fire global events as of now if asked to // Don't fire events if jQuery.event is undefined in an AMD-usage scenario (#15118) fireGlobals = jQuery.event && s.global; // Watch for a new set of requests if ( fireGlobals && jQuery.active++ === 0 ) { jQuery.event.trigger( "ajaxStart" ); } // Uppercase the type s.type = s.type.toUpperCase(); // Determine if request has content s.hasContent = !rnoContent.test( s.type ); // Save the URL in case we're toying with the If-Modified-Since // and/or If-None-Match header later on // Remove hash to simplify url manipulation cacheURL = s.url.replace( rhash, "" ); // More options handling for requests with no content if ( !s.hasContent ) { // Remember the hash so we can put it back uncached = s.url.slice( cacheURL.length ); // If data is available, append data to url if ( s.data ) { cacheURL += ( rquery.test( cacheURL ) ? "&" : "?" ) + s.data; // #9682: remove data so that it's not used in an eventual retry delete s.data; } // Add or update anti-cache param if needed if ( s.cache === false ) { cacheURL = cacheURL.replace( rantiCache, "$1" ); uncached = ( rquery.test( cacheURL ) ? "&" : "?" ) + "_=" + ( nonce++ ) + uncached; } // Put hash and anti-cache on the URL that will be requested (gh-1732) s.url = cacheURL + uncached; // Change '%20' to '+' if this is encoded form body content (gh-2658) } else if ( s.data && s.processData && ( s.contentType || "" ).indexOf( "application/x-www-form-urlencoded" ) === 0 ) { s.data = s.data.replace( r20, "+" ); } // Set the If-Modified-Since and/or If-None-Match header, if in ifModified mode. if ( s.ifModified ) { if ( jQuery.lastModified[ cacheURL ] ) { jqXHR.setRequestHeader( "If-Modified-Since", jQuery.lastModified[ cacheURL ] ); } if ( jQuery.etag[ cacheURL ] ) { jqXHR.setRequestHeader( "If-None-Match", jQuery.etag[ cacheURL ] ); } } // Set the correct header, if data is being sent if ( s.data && s.hasContent && s.contentType !== false || options.contentType ) { jqXHR.setRequestHeader( "Content-Type", s.contentType ); } // Set the Accepts header for the server, depending on the dataType jqXHR.setRequestHeader( "Accept", s.dataTypes[ 0 ] && s.accepts[ s.dataTypes[ 0 ] ] ? s.accepts[ s.dataTypes[ 0 ] ] + ( s.dataTypes[ 0 ] !== "*" ? ", " + allTypes + "; q=0.01" : "" ) : s.accepts[ "*" ] ); // Check for headers option for ( i in s.headers ) { jqXHR.setRequestHeader( i, s.headers[ i ] ); } // Allow custom headers/mimetypes and early abort if ( s.beforeSend && ( s.beforeSend.call( callbackContext, jqXHR, s ) === false || completed ) ) { // Abort if not done already and return return jqXHR.abort(); } // Aborting is no longer a cancellation strAbort = "abort"; // Install callbacks on deferreds completeDeferred.add( s.complete ); jqXHR.done( s.success ); jqXHR.fail( s.error ); // Get transport transport = inspectPrefiltersOrTransports( transports, s, options, jqXHR ); // If no transport, we auto-abort if ( !transport ) { done( -1, "No Transport" ); } else { jqXHR.readyState = 1; // Send global event if ( fireGlobals ) { globalEventContext.trigger( "ajaxSend", [ jqXHR, s ] ); } // If request was aborted inside ajaxSend, stop there if ( completed ) { return jqXHR; } // Timeout if ( s.async && s.timeout > 0 ) { timeoutTimer = window.setTimeout( function() { jqXHR.abort( "timeout" ); }, s.timeout ); } try { completed = false; transport.send( requestHeaders, done ); } catch ( e ) { // Rethrow post-completion exceptions if ( completed ) { throw e; } // Propagate others as results done( -1, e ); } } // Callback for when everything is done function done( status, nativeStatusText, responses, headers ) { var isSuccess, success, error, response, modified, statusText = nativeStatusText; // Ignore repeat invocations if ( completed ) { return; } completed = true; // Clear timeout if it exists if ( timeoutTimer ) { window.clearTimeout( timeoutTimer ); } // Dereference transport for early garbage collection // (no matter how long the jqXHR object will be used) transport = undefined; // Cache response headers responseHeadersString = headers || ""; // Set readyState jqXHR.readyState = status > 0 ? 4 : 0; // Determine if successful isSuccess = status >= 200 && status < 300 || status === 304; // Get response data if ( responses ) { response = ajaxHandleResponses( s, jqXHR, responses ); } // Convert no matter what (that way responseXXX fields are always set) response = ajaxConvert( s, response, jqXHR, isSuccess ); // If successful, handle type chaining if ( isSuccess ) { // Set the If-Modified-Since and/or If-None-Match header, if in ifModified mode. if ( s.ifModified ) { modified = jqXHR.getResponseHeader( "Last-Modified" ); if ( modified ) { jQuery.lastModified[ cacheURL ] = modified; } modified = jqXHR.getResponseHeader( "etag" ); if ( modified ) { jQuery.etag[ cacheURL ] = modified; } } // if no content if ( status === 204 || s.type === "HEAD" ) { statusText = "nocontent"; // if not modified } else if ( status === 304 ) { statusText = "notmodified"; // If we have data, let's convert it } else { statusText = response.state; success = response.data; error = response.error; isSuccess = !error; } } else { // Extract error from statusText and normalize for non-aborts error = statusText; if ( status || !statusText ) { statusText = "error"; if ( status < 0 ) { status = 0; } } } // Set data for the fake xhr object jqXHR.status = status; jqXHR.statusText = ( nativeStatusText || statusText ) + ""; // Success/Error if ( isSuccess ) { deferred.resolveWith( callbackContext, [ success, statusText, jqXHR ] ); } else { deferred.rejectWith( callbackContext, [ jqXHR, statusText, error ] ); } // Status-dependent callbacks jqXHR.statusCode( statusCode ); statusCode = undefined; if ( fireGlobals ) { globalEventContext.trigger( isSuccess ? "ajaxSuccess" : "ajaxError", [ jqXHR, s, isSuccess ? success : error ] ); } // Complete completeDeferred.fireWith( callbackContext, [ jqXHR, statusText ] ); if ( fireGlobals ) { globalEventContext.trigger( "ajaxComplete", [ jqXHR, s ] ); // Handle the global AJAX counter if ( !( --jQuery.active ) ) { jQuery.event.trigger( "ajaxStop" ); } } } return jqXHR; } 

Quindi sì, è ovviamente ridicolo provare a rimuovere tutte le dipendenze da questo codice. È meglio includere solo jQuery se si desidera utilizzare il metodo di jQuery per caricare script esterni in modo asincrono.

Oppure, considera di utilizzare uno strumento diverso del tutto.


16 luglio 2013 - dal jQuery budella senza dipendenze [citazione del codice sorgente necessaria]

 function getScript(src, callback) { var s = document.createElement('script'); s.src = src; s.async = true; s.onreadystatechange = s.onload = function() { if (!callback.done && (!s.readyState || /loaded|complete/.test(s.readyState))) { callback.done = true; callback(); } }; document.querySelector('head').appendChild(s); } 

Uno dei migliori schemi da utilizzare qui è utilizzare addEventListener per ascoltare un evento personalizzato come “MyScriptLoaded”. Quindi, modifica lo script incluso per triggersre questo evento come ultima azione. Ciò garantirà l’intervento solo dopo che il nuovo script è stato completamente caricato.

Se hai il controllo sulla sorgente del javascript che viene caricato, la soluzione migliore è quella di far eseguire a quel codice una pseudo-funzione di callback che esiste nel contesto della tua pagina. Questo è qualcosa come il metodo usato per JSONP. Quindi, immagina sulla tua pagina chiamante, hai questo:

 function createScript(src, id) { if (document.getElementById(id) == null) { var newScript = document.createElement('script'); newScript.setAttribute("type", "text/javascript"); newScript.setAttribute("src", src); newScript.setAttribute("id", id); document.getElementsByTagName("head")[0].appendChild(newScript); } } function callbackFunc() { // make use of new functions here.... } 

E ognuno dei tuoi file sorgente potrebbe finire con questa linea:

 callbackFunc();