如何利用JS代码选取textarea中的指定行

实例名称

选取textarea中的指定行

实例描述

使用控件的focus或select方法，可以很方便地选取textarea的所有内容，但却无法实现某行的选取。本例讲解如何选取textarea中的指定行。

实例代码

function getTxtRownum， mytxtu00a0u00a0 //获取指定行的方法-第二个参数为文本框IDu00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 //获取文本框内当前光标的位置u00a0u00a0u00a0 var range = ;u00a0u00a0u00a0 var rect = ;//返回一个矩形u00a0u00a0u00a0 var left = ;u00a0u00a0u00a0 ifnum - 1 || num 0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 return;u00a0u00a0u00a0 ifnum == 0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 //选择第一行的情况u00a0u00a0u00a0 u00a0u00a0u00a0u00a0u00a0 //设置选择范围u00a0u00a0u00a0u00a0u00a0u00a0 var right = ;u00a0u00a0u00a0u00a0u00a0u00a0 "character"，-;u00a0u00a0 u00a0u00a0u00a0u00a0u00a0u00a0 + rightu00a0u00a0u00a0u00a0u00a0u00a0 u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 "character";u00a0u00a0u00a0u00a0u00a0u00a0 u00a0u00a0u00a0u00a0u00a0u00a0 return range;u00a0u00a0u00a0 u00a0u00a0u00a0 elseu00a0u00a0u00a0 u00a0u00a0u00a0u00a0u00a0u00a0 //设置选择范围u00a0u00a0u00a0u00a0u00a0u00a0u00a0 var right = ;u00a0u00a0u00a0u00a0u00a0u00a0u00a0 var range = getTxtRownum - 1， mytxt;u00a0u00a0u00a0u00a0u00a0u00a0u00a0 "character"， + 1;u00a0u00a0u00a0u00a0u00a0u00a0u00a0 + rightu00a0u00a0u00a0u00a0u00a0u00a0u00a0 u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 "character";u00a0u00a0u00a0u00a0u00a0u00a0u00a0 u00a0u00a0u00a0u00a0u00a0u00a0u00a0 leftu00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 "character"，-1;u00a0u00a0u00a0u00a0u00a0u00a0u00a0 return range;u00a0u00a0u00a0 //选择指定行数的方法function getTextnumu00a0u00a0u00a0 var range = getTxtRownum，"txt"//调用真正的获取行方法u00a0u00a0u00a0 ifrange != nullu00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 //如果指定的行内容不为空u00a0u00a0u00a0 u00a0u00a0u00a0u00a0u00a0u00a0u00a0 ;u00a0u00a0u00a0u00a0u00a0u00a0u00a0 ;u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0u00a0 //选择指定的行u00a0u00a0u00a0 /SCRIPT

运行效果

难点剖析

本例的难点在于光标的获取，以及文本的选择范围。使用“createTextRange”方法获取文本中光标的位置。使用“getclientRects”选择一个范围，然后设置范围的起始位置和结束位置。最后使用“select”方法选择整行内容。

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