JQuery选择器之位置选择器

语法 描述 B:first 匹配页面上满足选择器B的第一个元素 B:last 匹配页面上满足选择器B的最后一个元素 B:first-child 所有匹配选择器B的第一个元素 B:last-child 所有匹配选择器B的所有最后一个元素 B:only-child 匹配选择器B的唯一元素。 B:nth-child(n) 匹配选择器B的第N个子元素，从1开始。 B:nth-child(odd,even) 匹配选择器B的奇数位，偶数位子元素 B:nth-child(Xn+Y) 匹配选择器B的第(Xn+Y)个子元素 B:even 所有偶数位匹配选择B的元素 B:odd 所有奇数位匹配选择B的元素 B:eq(n) 第N个匹配选择B的元素，从0开始 B:gt(n) 第N个元素之后匹配选择B的元素，从0开始 B:lt(n) 第N个元素之前匹配选择B的元素，从0开始

示例：

语句 说明 $(“p:first”) selects the first element on the page $(img[src§=.png]:first”) selects the first <img> element on the page that has a src attribute ending in .png $(“button.small:last”) selects the last <button> element on the page that has a class name of small $(“li:first-child”) selects all <li> elements that are first children within their lists $(“a:only-child”) selects all <a> elements that are the only element within their parent $(“li:nth-child(2)”) selects all <li> elements that are the second item within their lists $(“tr:nth-child(odd)”) selects all odd <tr> elements within a table $(“div:nth-child(5n)”) selects every 5th <div> element $(“div:nth-child(5n+1)”) selects the element after every 5th <div> element $(“.someClass:eq(1)”) selects the second element with a class name of someClass $(“.someClass:gt(1)”) selects all but the first two elements with a class name of someClass $(“.someClass:lt(4)”) selects the first four elements with a class name of someClass