动态加载外部javascript文件,并等待它加载 - 不使用JQuery [英] Dynamically load external javascript file, and wait for it to load - without using JQuery
问题描述
我正在尝试动态加载外部.js文件(根据我从用户那里得到的输入)。
目前我的代码如下所示:
I'm trying to dynamically load an external .js file (according to an input I get from the user). Currently my code looks like this:
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);
}
}
这种工作。它确实加载了脚本,但如果我尝试调用在新脚本中定义的函数,它将无法工作。奇怪的是,如果我等待一秒钟(使用警报(测试)
或类似的东西)脚本确实有效。
This kind of work. It does load the script, but if I try to call a function that is defined inside the new script it won't work. The weird thing is if I wait for a second (using an alert("test")
or something like that) the script does work.
我想这是因为浏览器会立即添加< script>
标签,但需要更长时间才能读取内部的脚本.js文件。
我尝试使用typeof testfunction ==='function'
进行一些变化,但没有运气。
I guess its because the browser adds the <script>
tag immediately, but it takes it a little longer to "read" the script inside of the .js file.
I tried playing with "typeof testfunction === 'function'"
with a few variations but no luck.
这样做的好方法是什么?
Any good way of doing this?
推荐答案
2017年2月21日 - jQuery如何做到
February 21, 2017 - how jQuery does it
jQuery.getScript
现在只是 jQuery.get
jQuery.getScript
is now just a wrapper for jQuery.get
getScript: function( url, callback ) {
return jQuery.get( url, undefined, callback, "script" );
}
jQuery.get
只是<$ c的包装器$ c> jQuery.ajax - 使用元编程定义... ...
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
是这个430+ LOC怪物
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;
}
所以是的,尝试从此删除所有依赖项显然是荒谬的码。如果你想使用jQuery的方法异步加载外部脚本,你最好只包括jQuery。
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.
或者,考虑一起使用不同的工具。
Or, consider using a different tool altogether.
2013年7月16日 - 来自没有依赖关系的jQuery guts [需要源代码引用]
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);
}
这篇关于动态加载外部javascript文件,并等待它加载 - 不使用JQuery的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!