February 21, 2017 – how jQuery does it
jQuery.getScript is now just a wrapper for jQuery.get
getScript: function( url, callback ) {
return jQuery.get( url, undefined, callback, "script" );
}
jQuery.get is just a wrapper of jQuery.ajax – it is defined using metaprogramming as …
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 is this 430+ LOC monster
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,
// e.g. 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;
}
So yeah, this is obviously ridiculous to try to remove all the dependencies from this code. You’re better off just including jQuery if you want to use jQuery’s method for loading external scripts asynchronously.
Or, consider using a different tool altogether.
July 16, 2013 – from jQuery guts with no dependencies [source code citation needed]
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);
}