JQuery.ajaxPrefilter case analysis
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JQuery.ajaxPrefilter ([dataTypes], handler (options, originalOptions, jqXHR))
Description: sent before each request and processed by $. Ajax () before they are processed, set custom Ajax options or modify existing options.
DataTypes
Type: String
An optional string containing one or more space-separated data types
Handler (options, originalOptions, jqXHR)
Type: Function ()
A handler that sets the default value for future Ajax requests.
Register a typical pre-filter that uses $.ajaxPrefilter (), which looks like this:
$.ajaxPrefilter (function (options, originalOptions, jqXHR) {
/ / Modify options, control originalOptions, store jqXHR, etc
})
Under the following circumstances:
Options is the requested option
The originalOptions value is provided as an unmodified option for the Ajax method, so there is no default value in the ajaxSettings setting
JqXHR is the requested jqXHR object
When customizing options that need to be handled in advance, the pre-filter (Prefilters) is a perfect choice. Given the following code, for example, if the custom abortOnRetry option is set to true, calling $.ajax () will automatically abort the request for the same URL:
Var currentRequests = {}
$.ajaxPrefilter (function (options, originalOptions, jqXHR) {
If (options.abortOnRetry) {
If (currentRequests [options.url]) {
CurrentRequests [options.url] .abort ()
}
CurrentRequests [options.url] = jqXHR
}
})
Pre-filters (Prefilters) can also be used to modify existing options. For example, the following proxy server requests http://mydomain.net/proxy/ across domains:
$.ajaxPrefilter (function (options) {
If (options.crossDomain) {
Options.url = "http://mydomain.net/proxy/" + encodeURIComponent (options.url)
Options.crossDomain = false
}
})
If an optional dataTypes parameter is provided, the prefilter (prefilter) will only be valid for requests that satisfy the specified dataTypes. For example, the following applies only to the pre-filters given by JSON and script requests:
$.ajaxPrefilter ("json script", function (options, originalOptions, jqXHR) {
/ / Modify options, control originalOptions, store jqXHR, etc
})
The $.ajaxPrefilter () method can also redirect the request to another data type and return that data type. For example, if the URL contains the specified property set in the isActuallyScript () function, then set to a request for "script":
$.ajaxPrefilter (function (options) {
If (isActuallyScript (options.url)) {
Return "script"
}
})
This ensures that the request is considered to be of type "script" and that all pre-filters that are valid for the script data type will also be applied to it.
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