jquery/src/core/init.js

JavaScript library for DOM operations

// Initialize a jQuery object
import { jQuery } from "../core.js";
import { document } from "../var/document.js";
import { rsingleTag } from "./var/rsingleTag.js";
import { isObviousHtml } from "./isObviousHtml.js";

import "../traversing/findFilter.js";

// A central reference to the root jQuery(document)
var rootjQuery,

	// A simple way to check for HTML strings
	// Prioritize #id over <tag> to avoid XSS via location.hash (trac-9521)
	// Strict HTML recognition (trac-11290: must start with <)
	// Shortcut simple #id case for speed
	rquickExpr = /^(?:\s*(<[\w\W]+>)[^>]*|#([\w-]+))$/,

	init = jQuery.fn.init = function( selector, context ) {
		var match, elem;

		// HANDLE: $(""), $(null), $(undefined), $(false)
		if ( !selector ) {
			return this;
		}

		// HANDLE: $(DOMElement)
		if ( selector.nodeType ) {
			this[ 0 ] = selector;
			this.length = 1;
			return this;

		// HANDLE: $(function)
		// Shortcut for document ready
		} else if ( typeof selector === "function" ) {
			return rootjQuery.ready !== undefined ?
				rootjQuery.ready( selector ) :

				// Execute immediately if ready is not present
				selector( jQuery );

		} else {

			// Handle obvious HTML strings
			match = selector + "";
			if ( isObviousHtml( match ) ) {

				// Assume that strings that start and end with <> are HTML and skip
				// the regex check. This also handles browser-supported HTML wrappers
				// like TrustedHTML.
				match = [ null, selector, null ];

			// Handle HTML strings or selectors
			} else if ( typeof selector === "string" ) {
				match = rquickExpr.exec( selector );
			} else {
				return jQuery.makeArray( selector, this );
			}

			// Match html or make sure no context is specified for #id
			// Note: match[1] may be a string or a TrustedHTML wrapper
			if ( match && ( match[ 1 ] || !context ) ) {

				// HANDLE: $(html) -> $(array)
				if ( match[ 1 ] ) {
					context = context instanceof jQuery ? context[ 0 ] : context;

					// Option to run scripts is true for back-compat
					// Intentionally let the error be thrown if parseHTML is not present
					jQuery.merge( this, jQuery.parseHTML(
						match[ 1 ],
						context && context.nodeType ? context.ownerDocument || context : document,
						true
					) );

					// HANDLE: $(html, props)
					if ( rsingleTag.test( match[ 1 ] ) && jQuery.isPlainObject( context ) ) {
						for ( match in context ) {

							// Properties of context are called as methods if possible
							if ( typeof this[ match ] === "function" ) {
								this[ match ]( context[ match ] );

							// ...and otherwise set as attributes
							} else {
								this.attr( match, context[ match ] );
							}
						}
					}

					return this;

				// HANDLE: $(#id)
				} else {
					elem = document.getElementById( match[ 2 ] );

					if ( elem ) {

						// Inject the element directly into the jQuery object
						this[ 0 ] = elem;
						this.length = 1;
					}
					return this;
				}

			// HANDLE: $(expr) & $(expr, $(...))
			} else if ( !context || context.jquery ) {
				return ( context || rootjQuery ).find( selector );

			// HANDLE: $(expr, context)
			// (which is just equivalent to: $(context).find(expr)
			} else {
				return this.constructor( context ).find( selector );
			}
		}

	};

// Give the init function the jQuery prototype for later instantiation
init.prototype = jQuery.fn;

// Initialize central reference
rootjQuery = jQuery( document );