src/core/init.js

// Initialize a jQuery object

define( [

    "../core",

    "../var/document",

    "./var/rsingleTag",

    "../traversing/findFilter"

], function( jQuery, document, rsingleTag ) {

"use strict";

// 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 (#9521)

    // Strict HTML recognition (#11290: must start with <)

    // Shortcut simple #id case for speed

    rquickExpr = /^(?:\s*(<[\w\W]+>)[^>]*|#([\w-]+))$/,

    init = jQuery.fn.init = function( selector, context, root ) {

        var match, elem;

        // HANDLE: $(""), $(null), $(undefined), $(false)

        if ( !selector ) {

            return this;

        }

        // Method init() accepts an alternate rootjQuery

        // so migrate can support jQuery.sub (gh-2101)

        root = root || rootjQuery;

        // Handle HTML strings

        if ( typeof selector === "string" ) {

            if ( selector[ 0 ] === "<" &&

                selector[ selector.length - 1 ] === ">" &&

                selector.length >= 3 ) {

                // Assume that strings that start and end with <> are HTML and skip the regex check

                match = [ null, selector, null ];

            } else {

                match = rquickExpr.exec( selector );

            }

            // Match html or make sure no context is specified for #id

            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 ( jQuery.isFunction( this[ match ] ) ) {

                                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, $(...))

            } else if ( !context || context.jquery ) {

                return ( context || root ).find( selector );

            // HANDLE: $(expr, context)

            // (which is just equivalent to: $(context).find(expr)

            } else {

                return this.constructor( context ).find( selector );

            }

        // HANDLE: $(DOMElement)

        } else if ( selector.nodeType ) {

            this[ 0 ] = selector;

            this.length = 1;

            return this;

        // HANDLE: $(function)

        // Shortcut for document ready

        } else if ( jQuery.isFunction( selector ) ) {

            return root.ready !== undefined ?

                root.ready( selector ) :

                // Execute immediately if ready is not present

                selector( jQuery );

        }

        return jQuery.makeArray( selector, this );

    };

// Give the init function the jQuery prototype for later instantiation

init.prototype = jQuery.fn;

// Initialize central reference

rootjQuery = jQuery( document );

return init;

} );