posTop参数属性

Sets or retrieves the top position of the object in the units specified by the top attribute.

dhtml语法

html	n/a
scripting	object.style.postop [ = itop ]

dhtml可能的值

iTop	Floating-point that specifies or receives any valid floating-point number that uses the same length units as the top attribute.

The property is read/write. The property has no default value. The Microsoft Cascading Style Sheets (CSS) extension is not inherited.

Expressions can be used in place of the preceding value(s), as of Microsoft® Internet Explorer 5. For more information, see about dynamic properties.

remarks

this property reflects the value of the cascading style sheets (css)?b>top attribute for positioned items. this property always returns zero for nonpositioned items because "top" has meaning only when the object is positioned. If the top attribute is not set, the posTop property returns zero. Use the offsettop property to calculate actual positions within the document area.

setting this property changes the value of the top position but leaves the units designator for the property unchanged.

unlike the top property, the postop property value is a floating-point number, not a string.

for more information about how to access the dimension and location of objects on the page through the dynamic html（动态html，即dhtml）燿ocument object model (dom), see measuring element dimension and location.

Examples

This example uses the posTop property to move the first img object up by 10 units.

<script language="jscript">
document.all.tags("IMG").item(0).style.posTop -= 10;
</SCRIPT>

This example uses a timer to change the value of the posTop in increments of 10.

<SCRIPT LANGUAGE="JScript">
function moveThis()
{
:
if (sphere.style.posLeft<900) {
sphere.style.posTop += 2;
sphere.style.posLeft += 2;
window.setTimeout("moveThis();", 1);
}
}
:
</SCRIPT>

This feature requires Microsoft® Internet Explorer 4.0 or later. Click the following icon to install the latest version. Then reload this page to view the sample.

是否符合公共标准

There is no public standard that applies to this property.

Applies To

A, ACRONYM, ADDRESS, APPLET, B, BASE, BASEFONT, BIG, BLOCKQUOTE, BODY, BUTTON, CAPTION, CENTER, CITE, CODE, COL, COLGROUP, COMMENT, CUSTOM, DD, defaults, DEL, DFN, DIR, DIV, DL, DT, EM, EMBED, FIELDSET, FONT, FORM, FRAME, FRAMESET, HEAD, hn, HR, I, IFRAME, IMG, INPUT type=button, INPUT type=checkbox, INPUT type=file, INPUT type=image, INPUT type=password, INPUT type=radio, INPUT type=reset, INPUT type=submit, INPUT type=text, INS, KBD, LABEL, LEGEND, LI, LINK, LISTING, MARQUEE, MENU, META, nextID, NOBR, OBJECT, OL, OPTION, P, PLAINTEXT, PRE, Q, RT, RUBY, runtimeStyle, S, SAMP, SCRIPT, SELECT, SMALL, SPAN, STRIKE, STRONG, style, SUB, SUP, TABLE, TBODY, TD, TEXTAREA, TFOOT, TH, THEAD, TITLE, TR, TT, U, UL, VAR, XMP

更多语法参考

pixelTop