jQuery对象初始化的传参方式

jQuery对象初始化的传参方式包括：

1.$(DOMElement)

2.$('<h1>...</h1>'), $('#id'), $('.class') 传入字符串, 这是最常见的形式, 这种传参数经常也传入第二个参数context指定上下文,其中context参数可以为$(...), DOMElement

3.$(function() {}); <===> $(document).ready(function() { });

4.$({selector : '.class', context : context}) <===> $('.class', context)

jQuery.fn = jQuery.prototype = {

    constructor: jQuery,

    init: function( selector, context, rootjQuery ) {

        var match, elem, ret, doc;

        // 处理$(""), $(null), $(undefined), $(false)这几种参数,直接返回this

        if ( !selector ) {

            return this;

        }

        // 当传参selector为DOM结点时,将context置为selector

        if ( selector.nodeType ) {

            this.context = this[0] = selector;

            this.length = 1;

            return this;

        }

        // Handle HTML strings

        // 当传入的selector参数为字符串时,

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

            if ( selector.charAt(0) === "<" && selector.charAt( 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;

                    doc = ( context && context.nodeType ? context.ownerDocument || context : document );

                    // scripts is true for back-compat

                    selector = jQuery.parseHTML( match[1], doc, true );

                    if ( rsingleTag.test( match[1] ) && jQuery.isPlainObject( context ) ) {

                        this.attr.call( selector, context, true );

                    }

                    return jQuery.merge( this, selector );

                // HANDLE: $(#id)

                } else {

                    elem = document.getElementById( match[2] );

                    // Check parentNode to catch when Blackberry 4.6 returns

                    // nodes that are no longer in the document #6963

                    if ( elem && elem.parentNode ) {

                        // Handle the case where IE and Opera return items

                        // by name instead of ID

                        if ( elem.id !== match[2] ) {

                            return rootjQuery.find( selector );

                        }

                        // Otherwise, we inject the element directly into the jQuery object

                        this.length = 1;

                        this[0] = elem;

                    }

                    this.context = document;

                    this.selector = selector;

                    return this;

                }

            // HANDLE: $(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 );

            }

        // HANDLE: $(function)

        // Shortcut for document ready

        // 当selector为function时相当于$(document).ready(selector);

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

            return rootjQuery.ready( selector );

        }

        // 当selector参数为{selector:'#id', context:document}之类时,重置属性selector和context

        if ( selector.selector !== undefined ) {

            this.selector = selector.selector;

            this.context = selector.context;

        }

        return jQuery.makeArray( selector, this );

    }

};

以上就是本文的全部内容了，希望大家能够喜欢。