本章节分享两段代码，它可以实现对文本框中指定文本内容的选中效果。

代码实例:

function getPos(el) {
  var range, textRange, duplicate
  el.focus()
  if ( el.selectionStart ) return el.selectionStart
  else if ( document.selection ) { // IE
    range = document.selection.createRange()
    if ( range == null ) return el.value.length
    textRange = el.createTextRange()
    duplicate = textRange.duplicate()
    textRange.moveToBookmark(range.getBookmark())
    duplicate.setEndPoint('EndToStart', textRange)
    return duplicate.text.length
  }
}
 
function setPos(el, pos) {
  var range
  el.focus()
  if ( el.setSelectionRange )
    el.setSelectionRange(pos, pos)
  else if ( el.createTextRange ) {
    range.collapse(true)
    range.moveEnd('character', pos)
    range.moveStart('character', pos)
    range.select()
  }
}