JezK

Edit File: api-request.js

/**
 * Thin jQuery.ajax wrapper for WP REST API requests.
 *
 * Currently only applies to requests that do not use the `wp-api.js` Backbone
 * client library, though this may change.  Serves several purposes:
 *
 * - Allows overriding these requests as needed by customized WP installations.
 * - Sends the REST API nonce as a request header.
 * - Allows specifying only an endpoint namespace/path instead of a full URL.
 *
 * @since 4.9.0
 * @since 5.6.0 Added overriding of the "PUT" and "DELETE" methods with "POST".
 *              Added an "application/json" Accept header to all requests.
 * @output wp-includes/js/api-request.js
 */

( function( $ ) {
	var wpApiSettings = window.wpApiSettings;

function apiRequest( options ) {
		options = apiRequest.buildAjaxOptions( options );
		return apiRequest.transport( options );
	}

apiRequest.buildAjaxOptions = function( options ) {
		var url = options.url;
		var path = options.path;
		var method = options.method;
		var namespaceTrimmed, endpointTrimmed, apiRoot;
		var headers, addNonceHeader, addAcceptHeader, headerName;

if (
			typeof options.namespace === 'string' &&
			typeof options.endpoint === 'string'
		) {
			namespaceTrimmed = options.namespace.replace( /^\/|\/$/g, '' );
			endpointTrimmed = options.endpoint.replace( /^\//, '' );
			if ( endpointTrimmed ) {
				path = namespaceTrimmed + '/' + endpointTrimmed;
			} else {
				path = namespaceTrimmed;
			}
		}
		if ( typeof path === 'string' ) {
			apiRoot = wpApiSettings.root;
			path = path.replace( /^\//, '' );

// API root may already include query parameter prefix
			// if site is configured to use plain permalinks.
			if ( 'string' === typeof apiRoot && -1 !== apiRoot.indexOf( '?' ) ) {
				path = path.replace( '?', '&' );
			}

url = apiRoot + path;
		}

// If ?_wpnonce=... is present, no need to add a nonce header.
		addNonceHeader = ! ( options.data && options.data._wpnonce );
		addAcceptHeader = true;

headers = options.headers || {};

for ( headerName in headers ) {
			if ( ! headers.hasOwnProperty( headerName ) ) {
				continue;
			}

// If an 'X-WP-Nonce' or 'Accept' header (or any case-insensitive variation
			// thereof) was specified, no need to add the header again.
			switch ( headerName.toLowerCase() ) {
				case 'x-wp-nonce':
					addNonceHeader = false;
					break;
				case 'accept':
					addAcceptHeader = false;
					break;
			}
		}

if ( addNonceHeader ) {
			// Do not mutate the original headers object, if any.
			headers = $.extend( {
				'X-WP-Nonce': wpApiSettings.nonce
			}, headers );
		}

if ( addAcceptHeader ) {
			headers = $.extend( {
				'Accept': 'application/json, */*;q=0.1'
			}, headers );
		}

if ( typeof method === 'string' ) {
			method = method.toUpperCase();

if ( 'PUT' === method || 'DELETE' === method ) {
				headers = $.extend( {
					'X-HTTP-Method-Override': method
				}, headers );

method = 'POST';
			}
		}

// Do not mutate the original options object.
		options = $.extend( {}, options, {
			headers: headers,
			url: url,
			method: method
		} );

delete options.path;
		delete options.namespace;
		delete options.endpoint;

return options;
	};

apiRequest.transport = $.ajax;

/** @namespace wp */
	window.wp = window.wp || {};
	window.wp.apiRequest = apiRequest;
} )( jQuery );

XML-RPC server accepts POST requests only.