var nodeHook, boolHook,
    rclass = /[\t\r\n\f]/g,
    rreturn = /\r/g,
    rfocusable = /^(?:input|select|textarea|button)$/i;

jQuery.fn.extend({
    attr: function( name, value ) {
//遍歷this
//arguments.length > 1,jQuery.attr(this[i],name,value),返回this
//arguments.length <= 1,jQuery.attr(this[i],name,value),返回this
 

        return jQuery.access( this, jQuery.attr, name, value, arguments.length > 1 );
    },

    removeAttr: function( name ) {
        return this.each(function() {
            jQuery.removeAttr( this, name );
        });
    },

    prop: function( name, value ) {
        return jQuery.access( this
 
, jQuery.prop, name, value, arguments.length > 1 );
    },

    removeProp: function( name ) {
        return this.each(function() {
            delete this[ jQuery.propFix[ name ] || name ];
        });
    },

    //$(‘.div1‘).addClass(‘box2 box3‘);
    addClass: function( value ) {
        var classes, elem, cur, clazz, j,
            i 
 
= 0,
            len = this.length,
            proceed = typeof value === "string" && value;//是字符串返回字符串，不是返回flase
        /*
            $(‘div‘).addClass( function(index){
                alert(index);
                return ‘box‘+index;
            });
        */
        if ( jQuery.isFunction( value ) ) {
            console.log(this);//這裏的this是jQuery對象，Object { 0: <div#div1.box>, 1: <div#div2.box>, 2: <div#div3.box>, length: 3},通過return ( context || rootjQuery ).find(‘.div1‘)原生方法獲得，裏面每一個是節點對象不是jQuery對象
            return this.each(function( j ) {
                console.log(this);//這裏不是jQuery對象是dom節點對象，<div id=‘div1‘></div>，<div id=‘div2‘></div>，<div id=‘div3‘></div>
                console.log(jQuery( this ));//jQuery( this )是jQuery對象，Object { 0: <div#div1.box>, context: <div#div1.box>, length: 1 }，Object { 0: <div#div2.box>, context: <div#div2.box>, length: 1 }，Object { 0: <div#div3.box>, context: <div#div3.box>, length: 1 }
                /*jQuery( this )走的是
                if ( selector.nodeType ) {//節點都有nodeType屬性
                this.context = this[0] = selector;
                this.length = 1;
                return this;*/
                jQuery( this ).addClass( value.call( this, j, this.className ) );
            });
        }
        if ( proceed ) {
            // 把字符串正則分割成數組
            classes = ( value || "" ).match( core_rnotwhite ) || [];
            for ( ; i < len; i++ ) {
                elem = this[ i ];
                //不是元素節點返回false，elem.className元素有沒有class屬性，有就合並（重復不合並），cur是之前的class
                cur = elem.nodeType === 1 && ( elem.className ?
                //非空格轉換成空格
                    ( " " + elem.className + " " ).replace( rclass, " " ) :
                    " "
                );
                if ( cur ) {
                    j = 0;
                    while ( (clazz = classes[j++]) ) {
                        if ( cur.indexOf( " " + clazz + " " ) < 0 ) {
                            cur += clazz + " ";
                        }
                    }//前後去空格
                    elem.className = jQuery.trim( cur );
                }
            }
        }
        return this;
    },

    removeClass: function( value ) {
        var classes, elem, cur, clazz, j,
            i = 0,
            len = this.length,
            //先執行&&再||，proceed為true參數長度是0刪除所有或者參數是字符串，為false傳的不是字符串
            proceed = arguments.length === 0 || typeof value === "string" && value;
        if ( jQuery.isFunction( value ) ) {
            return this.each(function( j ) {
                jQuery( this ).removeClass( value.call( this, j, this.className ) );
            });
        }
        if ( proceed ) {
            classes = ( value || "" ).match( core_rnotwhite ) || [];
            for ( ; i < len; i++ ) {
                elem = this[ i ];
                // This expression is here for better compressibility (see addClass)
                cur = elem.nodeType === 1 && ( elem.className ?
                    ( " " + elem.className + " " ).replace( rclass, " " ) :
                    ""
                );
                if ( cur ) {
                    j = 0;
                    while ( (clazz = classes[j++]) ) {
                        // Remove *all* instances
                        while ( cur.indexOf( " " + clazz + " " ) >= 0 ) {
                            cur = cur.replace( " " + clazz + " ", " " );
                        }
                    }
                    elem.className = value ? jQuery.trim( cur ) : "";
                }
            }
        }
        return this;
    },

    toggleClass: function( value, stateVal ) {
        var type = typeof value;
    //$(‘#div1‘).toggleClass(‘box2 box3‘,true);//有沒有都是add
    //$(‘#div1‘).toggleClass(‘box2 box3‘,false);//有沒有都是刪除
        if ( typeof stateVal === "boolean" && type === "string" ) {//真就添加，假就刪除
            return stateVal ? this.addClass( value ) : this.removeClass( value );
        }

        if ( jQuery.isFunction( value ) ) {
            return this.each(function( i ) {
                jQuery( this ).toggleClass( value.call(this, i, this.className, stateVal), stateVal );
            });
        }
        //$(‘#div1‘).toggleClass(‘box2 box3‘)
        return this.each(function() {
            if ( type === "string" ) {
                // toggle individual class names
                var className,
                    i = 0,
                    self = jQuery( this ),//轉成jQuery對象，hasClass是jQuery對象的方法。
                    //空格分割成數組
                    classNames = value.match( core_rnotwhite ) || [];

                while ( (className = classNames[ i++ ]) ) {
                    // check each className given, space separated list
                    if ( self.hasClass( className ) ) {
                        self.removeClass( className );
                    } else {
                        self.addClass( className );
                    }
                }

            // Toggle whole class name
            //$(‘#div1‘).toggleClass(false);
            } else if ( type === core_strundefined || type === "boolean" ) {
                if ( this.className ) {
                    // store className if set
                    data_priv.set( this, "__className__", this.className );
                }

                // If the element has a class name or if we‘re passed "false",
                // then remove the whole classname (if there was one, the above saved it).
                // Otherwise bring back whatever was previously saved (if anything),
                // falling back to the empty string if nothing was stored.
                this.className = this.className || value === false ? "" : data_priv.get( this, "__className__" ) || "";
            }
        });
    },

    hasClass: function( selector ) {
        var className = " " + selector + " ",
            i = 0,
            l = this.length;
        for ( ; i < l; i++ ) {
            if ( this[i].nodeType === 1 && (" " + this[i].className + " ").replace(rclass, " ").indexOf( className ) >= 0 ) {
                return true;
            }
        }

        return false;
    },

    val: function( value ) {
        var hooks, ret, isFunction,
            elem = this[0];
        //$(‘#input1‘).val()
        if ( !arguments.length ) {//獲取
            if ( elem ) {//只獲取第一個元素
            //hooks兼容處理,jQuery.valHooks[ elem.type ]在valHooks 這個json中找不到就找jQuery.valHooks[ elem.nodeName.toLowerCase() ]
                hooks = jQuery.valHooks[ elem.type ] || jQuery.valHooks[ elem.nodeName.toLowerCase() ];
/*
valHooks: {
hooks = option: {   //elem.type || elem.nodeName.toLowerCase()
            get: function( elem ) {}
        },
hooks = select: {
            get: function( elem ) {},
            set: function( elem, value ) {}
        }
        下面的：
hooks = radio: { 
            set: function( elem ) {}
            get: function( elem, value ) {}
        },
hooks = checkbox: {
            set: function( elem ) {},
            get: function( elem, value ) {}
        }        
}
*/
                if ( hooks && "get" in hooks && (ret = hooks.get( elem, "value" )) !== undefined ) {
                    return ret;
                }
                //不再hooks裏面
                ret = elem.value;

                return typeof ret === "string" ?
                    // handle most common string cases
                    ret.replace(rreturn, "") :
                    // handle cases where value is null/undef or number
                    ret == null ? "" : ret;
            }

            return;
        }
        //設置
        isFunction = jQuery.isFunction( value );

        return this.each(function( i ) {
            var val;
            if ( this.nodeType !== 1 ) {
                return;
            }
            if ( isFunction ) {
                val = value.call( this, i, jQuery( this ).val() );
            } else {
                val = value;
            }
            // Treat null/undefined as ""; convert numbers to string
            if ( val == null ) {//$(‘#input1‘).val(null);
                val = "";
            } else if ( typeof val === "number" ) {//$(‘#input1‘).val(123123);
                val += "";//轉成字符串
            } else if ( jQuery.isArray( val ) ) {//$(‘#input2‘).val([‘hello‘]);
                val = jQuery.map(val, function ( value ) {
                    return value == null ? "" : value + "";
                });
            }
            hooks = jQuery.valHooks[ this.type ] || jQuery.valHooks[ this.nodeName.toLowerCase() ];
            // If set returns undefined, fall back to normal setting
            if ( !hooks || !("set" in hooks) || hooks.set( this, val, "value" ) === undefined ) {
                this.value = val;
            }
        });
    }
});

jQuery.extend({//靜態屬性只能通過jQuery靜態方式調
    valHooks: {//option-get,select-get.select-set  兼容性處理
        option: {
            get: function( elem ) {
                // attributes.value is undefined in Blackberry 4.7 but
                // uses .value. See #6932
                var val = elem.attributes.value;
                //val不存在輸出elem.value，val存在specified為false走elem.text
                return !val || val.specified ? elem.value : elem.text;
            }
        },
        select: {
            //$(‘select‘).val()
            get: function( elem ) {
                var value, option,
                    options = elem.options,//下拉選項
                    index = elem.selectedIndex,//當前索引值
                    //select只選了一個或者沒有選，one為true,就是單選
                    one = elem.type === "select-one" || index < 0,
                    //one為true時單選values是空，one是false時多選values是一個數組存儲所有的選擇的多個
                    values = one ? null : [],
                    //單選時max是當前索引加1，多選時是下拉選項的長度
                    max = one ? index + 1 : options.length,
                    //
                    i = index < 0 ?
                        max /*index < 0沒有選擇時one=true,i=max=0*/ 
                        :one ? 
                        index/*index >= 0有選擇時,select-one單選one=true,i=index,max=index+1，*/ 
                        :0   /*index >= 0有選擇時,不是select-one多選one=false,i=0,max=options.length*/
                    ;

                // 沒有選擇不進入循環，不獲取select的val()
                //有選擇單選，i=index,只獲取index的val()
                //有選擇好多選，全部獲取
                for ( ; i < max; i++ ) {
                    option = options[ i ];//js對象

                    // IE6-9 doesn‘t update selected after form reset (#2551)
                    if ( ( option.selected || i === index ) &&
                            // Don‘t return options that are disabled or in a disabled optgroup
                            ( jQuery.support.optDisabled ? !option.disabled : option.getAttribute("disabled") === null ) &&
                            ( !option.parentNode.disabled || !jQuery.nodeName( option.parentNode, "optgroup" ) ) ) {

                        // Get the specific value for the option
                        value = jQuery( option ).val();//轉成jQuery對象

                        // We don‘t need an array for one selects
                        if ( one ) {
                            return value;
                        }

                        // Multi-Selects return an array
                        values.push( value );
                    }
                }

                return values;
            },
            //    $(‘#select‘).val(111);//111被選中了
            set: function( elem, value ) {
                var optionSet, option,
                    options = elem.options,//所有的下拉選項，js對象
                    values = jQuery.makeArray( value ),//轉成數組
                    i = options.length;

                while ( i-- ) {//遍歷
                    option = options[ i ];
                    if ( (option.selected = jQuery.inArray( jQuery(option).val(), values ) >= 0) ) {//在數組裏面就把她設為選中
                        optionSet = true;
                    }
                }

                // force browsers to behave consistently when non-matching value is set
                if ( !optionSet ) {//都沒有
                    elem.selectedIndex = -1;
                }
                return values;
            }
        }
    },

    attr: function( elem, name, value ) {
        var hooks, ret,
            nType = elem.nodeType;

        // 節點不存在，或者文本、屬性、註釋節點
        if ( !elem || nType === 3 || nType === 8 || nType === 2 ) {
            return;
        }

        // core_strundefined = typeof undefined,
        if ( typeof elem.getAttribute === core_strundefined ) {
            //$(document).attr(‘title‘,‘hello‘); 走這裏通過.設置
            return jQuery.prop( elem, name, value );
        }

        // 1是元素節點，
        if ( nType !== 1 || !jQuery.isXMLDoc( elem ) ) {
            name = name.toLowerCase();
            //只有type才做兼容性處理
            hooks = jQuery.attrHooks[ name ] ||
            //$(‘input‘).attr(‘checked‘,true);//沒問題，做兼容了
                ( jQuery.expr.match.bool.test( name ) ? boolHook : nodeHook );
        }

        if ( value !== undefined ) {//設置
//$(‘#div1‘).attr(‘miaov‘，null); 調用remove
            if ( value === null ) {
                jQuery.removeAttr( elem, name );
//hooks中，set方法存在，就調用set方法並且返回值存在，就返回返回值
            } else if ( hooks && "set" in hooks && (ret = hooks.set( elem, value, name )) !== undefined ) {
                return ret;//有兼容性執行兼容操作，返回值

            } else {//沒有兼容性操作設置值
                elem.setAttribute( name, value + "" );
                return value;
            }
//hooks中，get方法存在，就調用get方法並且返回值存在，就返回返回值
        } else if ( hooks && "get" in hooks && (ret = hooks.get( elem, name )) !== null ) {//獲取，有兼容性返回值
            return ret;

        } else {//獲取沒有兼容性時
            ret = jQuery.find.attr( elem, name );

            // Non-existent attributes return null, we normalize to undefined
            return ret == null ?
                undefined :
                ret;
        }
    },

    removeAttr: function( elem, value ) {
        var name, propName,
            i = 0,
            //$(‘#div1‘).removeAttr(‘maio href id‘);
            attrNames = value && value.match( core_rnotwhite );//core_rnotwhite = /\S+/g, 非空格，返回數組

        if ( attrNames && elem.nodeType === 1 ) {
            while ( (name = attrNames[i++]) ) {
                /*
                propFix: {
                    "for": "htmlFor",
                    "class": "className"
                },
                *///  $(‘#div1‘).removeAttr(‘class‘);
                propName = jQuery.propFix[ name ] || name;

                // Boolean attributes get special treatment (#10870)
                if ( jQuery.expr.match.bool.test( name ) ) {
                    // $(‘#div1‘).removeAttr(‘checked‘);
                    elem[ propName ] = false;
                }

                elem.removeAttribute( name );//調用原生
            }
        }
    },
//hooks = jQuery.attrHooks[ name ]
    attrHooks: {
        type: {//只有name = ‘type‘,才會有有兼容性判斷。
            set: function( elem, value ) {//只有set說明兼容只是針對設置沒有獲取
                if ( !jQuery.support.radioValue && value === "radio" && jQuery.nodeName(elem, "input") ) {//單選值的兼容
                    // Setting the type on a radio button after the value resets the value in IE6-9
                    // Reset value to default in case type is set after value during creation
                    
                    //當設置type = ‘radio‘時IE會有兼容性問題，所以要先設置類型才設置值
                    var val = elem.value;
                    elem.setAttribute( "type", value );
                    if ( val ) {
                        elem.value = val;
                    }
                    return value;
                }
            }
        }
    },

    propFix: {
        "for": "htmlFor",
        "class": "className"
    },

    prop: function( elem, name, value ) {
        var ret, hooks, notxml,
            nType = elem.nodeType;

        // don‘t get/set properties on text, comment and attribute nodes
        if ( !elem || nType === 3 || nType === 8 || nType === 2 ) {
            return;
        }

        notxml = nType !== 1 || !jQuery.isXMLDoc( elem );

        if ( notxml ) {
            // Fix name and attach hooks
            name = jQuery.propFix[ name ] || name;
            hooks = jQuery.propHooks[ name ];//兼容性處理
        }

        if ( value !== undefined ) {//設置值
            return hooks && "set" in hooks && (ret = hooks.set( elem, value, name )) !== undefined ?
                ret :
                ( elem[ name ] = value );//prop使用的是.操作

        } else {//獲取值
            return hooks && "get" in hooks && (ret = hooks.get( elem, name )) !== null ?
                ret :
                elem[ name ];
        }
    },

    propHooks: {
        tabIndex: {//光標切換順序，只對tabIndex屬性做兼容
            get: function( elem ) {//只對get方法做兼容
                return elem.hasAttribute( "tabindex" ) || rfocusable.test( elem.nodeName ) || elem.href ?
                    elem.tabIndex :
                    -1;
            }
        }
    }
});

// Hooks for boolean attributes
boolHook = {
    set: function( elem, value, name ) {
        if ( value === false ) {
            // Remove boolean attributes when set to false
            jQuery.removeAttr( elem, name );
        } else {
            elem.setAttribute( name, name );
        }
        return name;
    }
};
jQuery.each( jQuery.expr.match.bool.source.match( /\w+/g ), function( i, name ) {
    var getter = jQuery.expr.attrHandle[ name ] || jQuery.find.attr;

    jQuery.expr.attrHandle[ name ] = function( elem, name, isXML ) {
        var fn = jQuery.expr.attrHandle[ name ],
            ret = isXML ?
                undefined :
                /* jshint eqeqeq: false */
                // Temporarily disable this handler to check existence
                (jQuery.expr.attrHandle[ name ] = undefined) !=
                    getter( elem, name, isXML ) ?

                    name.toLowerCase() :
                    null;

        // Restore handler
        jQuery.expr.attrHandle[ name ] = fn;

        return ret;
    };
});

// Support: IE9+
// Selectedness for an option in an optgroup can be inaccurate
if ( !jQuery.support.optSelected ) {
    jQuery.propHooks.selected = {
        get: function( elem ) {
            var parent = elem.parentNode;
            if ( parent && parent.parentNode ) {
                parent.parentNode.selectedIndex;
            }
            return null;
        }
    };
}

jQuery.each([
    "tabIndex",
    "readOnly",
    "maxLength",
    "cellSpacing",
    "cellPadding",
    "rowSpan",
    "colSpan",
    "useMap",
    "frameBorder",
    "contentEditable"
], function() {
    //value = callback.call( obj[ i ], i, obj[ i ] );
    jQuery.propFix[ this.toLowerCase() ] = this;
});

/*
valHooks: {
hooks = radio: { 
            set: function( elem ) {}
            get: function( elem, value ) {}
        },
hooks = checkbox: {
            set: function( elem ) {},
            get: function( elem, value ) {}
        }
}
*/
jQuery.each([ "radio", "checkbox" ], function() {
    jQuery.valHooks[ this ] = {
        //$(‘#radio‘).val([‘hello‘]);
        set: function( elem, value ) {
            if ( jQuery.isArray( value ) ) {
                return ( elem.checked = jQuery.inArray( jQuery(elem).val(), value ) >= 0 );//設置選中狀態
            }
        }
    };
    if ( !jQuery.support.checkOn ) {
    //有的話做處理，沒有不做處理    //獲取單選框和復選框的value值時絕大多數瀏覽器返回的都是on，有些是空的，
        jQuery.valHooks[ this ].get = function( elem ) {
            // Support: Webkit
            // "" is returned instead of "on" if a value isn‘t specified
            return elem.getAttribute("value") === null ? "on" : elem.value;
        };
    }
});

jQuery07源碼 (3803 , 4299) attr() prop() val() addClass()等 : 對元素屬性的操作