jquery源码12 offset() : 位置和尺寸的方法

// Back Compat <1.8 extension point
jQuery.fx.step = {};

if ( jQuery.expr && jQuery.expr.filters ) {
    jQuery.expr.filters.animated = function( elem ) {
        return jQuery.grep(jQuery.timers, function( fn ) {
            return elem === fn.elem;
        }).length;
    };
}
jQuery.fn.offset = function( options ) {
    if ( arguments.length ) {//设置
        return options === undefined ?
            this :
            this.each(function( i ) {//每一个元素设置
                jQuery.offset.setOffset( this, options, i );
            });
    }
//获取
    var docElem, win,
        elem = this[ 0 ],
        box = { top: 0, left: 0 },
        doc = elem && elem.ownerDocument;//document

    if ( !doc ) {
        return;
    }

    docElem = doc.documentElement;//html标签

    // Make sure it's not a disconnected DOM node
    if ( !jQuery.contains( docElem, elem ) ) {
        return box;
    }

    // getBoundingClientRect()得到一些属性值:ClientRect {top: 8, right: 58, bottom: 58, left: 8, width: 50…},是到可视区的不包含滚动区域，
    if ( typeof elem.getBoundingClientRect !== core_strundefined ) {
        box = elem.getBoundingClientRect();
    }
    win = getWindow( doc );//获取window
    //pageYOffset是y轴的滚动距离，clientTop边框宽度，
    return {
        top: box.top + win.pageYOffset - docElem.clientTop,
        left: box.left + win.pageXOffset - docElem.clientLeft
    };
};

jQuery.offset = {
//设置offset
    setOffset: function( elem, options, i ) {
        var curPosition, curLeft, curCSSTop, curTop, curOffset, curCSSLeft, calculatePosition,
            position = jQuery.css( elem, "position" ),//获取元素的position属性，
            curElem = jQuery( elem ),
            props = {};

        // Set position first, in-case top/left are set even on static elem
        if ( position === "static" ) {//没有定位就加一个相对定位
            elem.style.position = "relative";
        }

        curOffset = curElem.offset();
        curCSSTop = jQuery.css( elem, "top" );
        curCSSLeft = jQuery.css( elem, "left" );
        calculatePosition = ( position === "absolute" || position === "fixed" ) && ( curCSSTop + curCSSLeft ).indexOf("auto") > -1;

        // Need to be able to calculate position if either top or left is auto and position is either absolute or fixed
        if ( calculatePosition ) {
            curPosition = curElem.position();
            curTop = curPosition.top;
            curLeft = curPosition.left;

        } else {
            curTop = parseFloat( curCSSTop ) || 0;
            curLeft = parseFloat( curCSSLeft ) || 0;
        }

        if ( jQuery.isFunction( options ) ) {
            options = options.call( elem, i, curOffset );
        }

        if ( options.top != null ) {
            props.top = ( options.top - curOffset.top ) + curTop;
        }
        if ( options.left != null ) {
            props.left = ( options.left - curOffset.left ) + curLeft;
        }

        if ( "using" in options ) {
            options.using.call( elem, props );

        } else {
            curElem.css( props );
        }
    }
};

jQuery.fn.extend({

    position: function() {//获取
        if ( !this[ 0 ] ) {
            return;
        }

        var offsetParent, offset,
            elem = this[ 0 ],
            parentOffset = { top: 0, left: 0 };

        // Fixed elements are offset from window (parentOffset = {top:0, left: 0}, because it is it's only offset parent
        if ( jQuery.css( elem, "position" ) === "fixed" ) {
            // We assume that getBoundingClientRect is available when computed position is fixed
            offset = elem.getBoundingClientRect();

        } else {
            // 原生方法找父级
            offsetParent = this.offsetParent();

            // Get correct offsets
            offset = this.offset();
            if ( !jQuery.nodeName( offsetParent[ 0 ], "html" ) ) {
                parentOffset = offsetParent.offset();
            }

            // Add offsetParent borders
            parentOffset.top += jQuery.css( offsetParent[ 0 ], "borderTopWidth", true );
            parentOffset.left += jQuery.css( offsetParent[ 0 ], "borderLeftWidth", true );
        }

        // 自己的top减去父级的top
        return {
            top: offset.top - parentOffset.top - jQuery.css( elem, "marginTop", true ),
            left: offset.left - parentOffset.left - jQuery.css( elem, "marginLeft", true )
        };
    },

    offsetParent: function() {
        return this.map(function() {
            var offsetParent = this.offsetParent || docElem;

            while ( offsetParent && ( !jQuery.nodeName( offsetParent, "html" ) && jQuery.css( offsetParent, "position") === "static" ) ) {
                offsetParent = offsetParent.offsetParent;
            }

            return offsetParent || docElem;
        });
    }
});

// Create scrollLeft and scrollTop methods
jQuery.each( {scrollLeft: "pageXOffset", scrollTop: "pageYOffset"}, function( method, prop ) {
    var top = "pageYOffset" === prop;

    jQuery.fn[ method ] = function( val ) {
        return jQuery.access( this, function( elem, method, val ) {
            var win = getWindow( elem );

            if ( val === undefined ) {
                return win ? win[ prop ] : elem[ method ];
            }

            if ( win ) {
                win.scrollTo(
                    !top ? val : window.pageXOffset,
                    top ? val : window.pageYOffset
                );

            } else {
                elem[ method ] = val;//原生的方法
            }
        }, method, val, arguments.length, null );
    };
});

function getWindow( elem ) {
    return jQuery.isWindow( elem ) ? elem : elem.nodeType === 9 && elem.defaultView;
}
// Create innerHeight, innerWidth, height, width, outerHeight and outerWidth methods
jQuery.each( { Height: "height", Width: "width" }, function( name, type ) {
    jQuery.each( { padding: "inner" + name, content: type, "": "outer" + name }, function( defaultExtra, funcName ) {
        // margin is only for outerHeight, outerWidth
        jQuery.fn[ funcName ] = function( margin, value ) {
            var chainable = arguments.length && ( defaultExtra || typeof margin !== "boolean" ),
                extra = defaultExtra || ( margin === true || value === true ? "margin" : "border" );

            return jQuery.access( this, function( elem, type, value ) {
                var doc;
                //是window就得到可视区的宽高
                if ( jQuery.isWindow( elem ) ) {
                    // As of 5/8/2012 this will yield incorrect results for Mobile Safari, but there
                    // isn't a whole lot we can do. See pull request at this URL for discussion:
                    // https://github.com/jquery/jquery/pull/764
                    return elem.document.documentElement[ "client" + name ];
                }

                //是document就得到页面的宽高
                if ( elem.nodeType === 9 ) {
                    doc = elem.documentElement;

                    // Either scroll[Width/Height] or offset[Width/Height] or client[Width/Height],
                    // whichever is greatest
                    return Math.max(
                        elem.body[ "scroll" + name ], doc[ "scroll" + name ],
                        elem.body[ "offset" + name ], doc[ "offset" + name ],
                        doc[ "client" + name ]
                    );
                }

                return value === undefined ?
                    jQuery.css( elem, type, extra ) ://css方式获取

                    jQuery.style( elem, type, value, extra );//style方式获取
            }, type, chainable ? margin : undefined, chainable, null );
        };
    });
});
// Limit scope pollution from any deprecated API
// (function() {

// The number of elements contained in the matched element set
jQuery.fn.size = function() {
    return this.length;
};

jQuery.fn.andSelf = jQuery.fn.addBack;

// })();
if ( typeof module === "object" && module && typeof module.exports === "object" ) {
    // Expose jQuery as module.exports in loaders that implement the Node
    // module pattern (including browserify). Do not create the global, since
    // the user will be storing it themselves locally, and globals are frowned
    // upon in the Node module world.
    module.exports = jQuery;
} else {
    // Register as a named AMD module, since jQuery can be concatenated with other
    // files that may use define, but not via a proper concatenation script that
    // understands anonymous AMD modules. A named AMD is safest and most robust
    // way to register. Lowercase jquery is used because AMD module names are
    // derived from file names, and jQuery is normally delivered in a lowercase
    // file name. Do this after creating the global so that if an AMD module wants
    // to call noConflict to hide this version of jQuery, it will work.
    if ( typeof define === "function" && define.amd ) {
        define( "jquery", [], function () { return jQuery; } );
    }
}

// If there is a window object, that at least has a document property,
// define jQuery and $ identifiers
if ( typeof window === "object" && typeof window.document === "object" ) {
    window.jQuery = window.$ = jQuery;
}

})( window );

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>sss</title>
<script src="jquery-203.js"></script>
</head>
<body>
<script>
window.onload = function(){

    console.log( $('#div1').offset().left );//到屏幕左边的距离。不看父节点有没有定位

    console.log( $('#div2').position().left );//到屏幕左边的距离。相对于有定位的父级,不计算margin值

    $('#div2').position( {left:100,top:100} );//会自动加一个相对定位

    console.log($('#div2').get(0).getBoundingClientRect());//ClientRect {top: 8, right: 58, bottom: 58, left: 8, width: 50…},是到可视区的不包含滚动区域，

}
</script>
</head>

<body>

<div id="div1" style="width:100px;height:100px;background-color:yellow;posotion:relative;">
    <div id='div2' style="width:50px;height:50px;background-color:red;position:left;left:10;top:10" >

    </div>
</div>
</body>
</html>