了解如何使用JavaScript选择textarea

Question

我正在使用textarea内的浏览器内编辑器。我已经开始寻找处理textarea选择的一些信息，并发现this jQuery plugin, fieldSelection做了一些简单的操作。

但是，它没有解释发生了什么。

我想了解更多关于textarea选择的JavaScript，最好是描述DOM3之前和DOM30之后的场景。

Answer 1

从PPK的introduction to ranges开始。 Mozilla开发者连接有关于W3C selections的信息。微软有他们的系统documented on MSDN。一些更多的技巧可以发现in the answers here。

除了不兼容的接口之外，您会很高兴知道textarea节点还有额外的奇怪之处。如果我没有记错的话，当你在IE中选择它们时，它们的行为与其他节点相同，但在其他浏览器中，它们有一个独立的选择范围，通过节点上的.selectionEnd和.selectionStart属性公开。

此外，你应该真的看看.contentEdiable作为一种手段来编辑生活的东西。从Firefox3发布以来，所有浏览器都支持这一功能。

Answer 2

function get_selection(the_id) 
{ 
    var e = document.getElementById(the_id); 

    //Mozilla and DOM 3.0 
    if('selectionStart' in e) 
    { 
     var l = e.selectionEnd - e.selectionStart; 
     return { start: e.selectionStart, end: e.selectionEnd, length: l, text: e.value.substr(e.selectionStart, l) }; 
    } 
    //IE 
    else if(document.selection) 
    { 
     e.focus(); 
     var r = document.selection.createRange(); 
     var tr = e.createTextRange(); 
     var tr2 = tr.duplicate(); 
     tr2.moveToBookmark(r.getBookmark()); 
     tr.setEndPoint('EndToStart',tr2); 
     if (r == null || tr == null) return { start: e.value.length, end: e.value.length, length: 0, text: '' }; 
     var text_part = r.text.replace(/[\r\n]/g,'.'); //for some reason IE doesn't always count the \n and \r in the length 
     var text_whole = e.value.replace(/[\r\n]/g,'.'); 
     var the_start = text_whole.indexOf(text_part,tr.text.length); 
     return { start: the_start, end: the_start + text_part.length, length: text_part.length, text: r.text }; 
    } 
    //Browser not supported 
    else return { start: e.value.length, end: e.value.length, length: 0, text: '' }; 
} 

function replace_selection(the_id,replace_str) 
{ 
    var e = document.getElementById(the_id); 
    selection = get_selection(the_id); 
    var start_pos = selection.start; 
    var end_pos = start_pos + replace_str.length; 
    e.value = e.value.substr(0, start_pos) + replace_str + e.value.substr(selection.end, e.value.length); 
    set_selection(the_id,start_pos,end_pos); 
    return {start: start_pos, end: end_pos, length: replace_str.length, text: replace_str}; 
} 

function set_selection(the_id,start_pos,end_pos) 
{ 
    var e = document.getElementById(the_id); 

    //Mozilla and DOM 3.0 
    if('selectionStart' in e) 
    { 
     e.focus(); 
     e.selectionStart = start_pos; 
     e.selectionEnd = end_pos; 
    } 
    //IE 
    else if(document.selection) 
    { 
     e.focus(); 
     var tr = e.createTextRange(); 

     //Fix IE from counting the newline characters as two seperate characters 
     var stop_it = start_pos; 
     for (i=0; i < stop_it; i++) if(e.value[i].search(/[\r\n]/) != -1) start_pos = start_pos - .5; 
     stop_it = end_pos; 
     for (i=0; i < stop_it; i++) if(e.value[i].search(/[\r\n]/) != -1) end_pos = end_pos - .5; 

     tr.moveEnd('textedit',-1); 
     tr.moveStart('character',start_pos); 
     tr.moveEnd('character',end_pos - start_pos); 
     tr.select(); 
    } 
    return get_selection(the_id); 
} 

function wrap_selection(the_id, left_str, right_str, sel_offset, sel_length) 
{ 
    var the_sel_text = get_selection(the_id).text; 
    var selection = replace_selection(the_id, left_str + the_sel_text + right_str); 
    if(sel_offset !== undefined && sel_length !== undefined) selection = set_selection(the_id, selection.start + sel_offset, selection.start + sel_offset + sel_length); 
    else if(the_sel_text == '') selection = set_selection(the_id, selection.start + left_str.length, selection.start + left_str.length); 
    return selection; 
} 

Answer 3

我唯一可以补充的是，它似乎（并没有真正尝试它），这应该滚动一直向上滚动，只要你处理内容。一个EAY的补救办法是换行不

e.value = 

行两行复制和恢复scrollTop的，就像这样：

var rememberScrollTop = e.scrollTop; 
e.value = .... (same as in user357565 snippet) 
e.scrollTop = rememberScrollTop; 

Answer 4

我刚刚通过user357565提出的解决方案，并为重新编码jQuery直接使用：

(function ($) { 
    $.fn.get_selection = function() { 
    var e = this.get(0); 
    //Mozilla and DOM 3.0 
    if('selectionStart' in e) { 
     var l = e.selectionEnd - e.selectionStart; 
     return { start: e.selectionStart, end: e.selectionEnd, length: l, text: e.value.substr(e.selectionStart, l) }; 
    } 
    else if(document.selection) { //IE 
     e.focus(); 
     var r = document.selection.createRange(); 
     var tr = e.createTextRange(); 
     var tr2 = tr.duplicate(); 
     tr2.moveToBookmark(r.getBookmark()); 
     tr.setEndPoint('EndToStart',tr2); 
     if (r == null || tr == null) return { start: e.value.length, end: e.value.length, length: 0, text: '' }; 
     var text_part = r.text.replace(/[\r\n]/g,'.'); //for some reason IE doesn't always count the \n and \r in length 
     var text_whole = e.value.replace(/[\r\n]/g,'.'); 
     var the_start = text_whole.indexOf(text_part,tr.text.length); 
     return { start: the_start, end: the_start + text_part.length, length: text_part.length, text: r.text }; 
    } 
    //Browser not supported 
    else return { start: e.value.length, end: e.value.length, length: 0, text: '' }; 
    }; 

    $.fn.set_selection = function (start_pos,end_pos) { 
    var e = this.get(0); 
    //Mozilla and DOM 3.0 
    if('selectionStart' in e) { 
     e.focus(); 
     e.selectionStart = start_pos; 
     e.selectionEnd = end_pos; 
    } 
    else if (document.selection) { //IE 
     e.focus(); 
     var tr = e.createTextRange(); 

     //Fix IE from counting the newline characters as two seperate characters 
     var stop_it = start_pos; 
     for (i=0; i < stop_it; i++) if(e.value[i].search(/[\r\n]/) != -1) start_pos = start_pos - .5; 
     stop_it = end_pos; 
     for (i=0; i < stop_it; i++) if(e.value[i].search(/[\r\n]/) != -1) end_pos = end_pos - .5; 

     tr.moveEnd('textedit',-1); 
     tr.moveStart('character',start_pos); 
     tr.moveEnd('character',end_pos - start_pos); 
     tr.select(); 
    } 
    return this.get_selection(); 
    }; 

    $.fn.replace_selection = function (replace_str) { 
    var e = this.get(0); 
    selection = this.get_selection(); 
    var start_pos = selection.start; 
    var end_pos = start_pos + replace_str.length; 
    e.value = e.value.substr(0, start_pos) + replace_str + e.value.substr(selection.end, e.value.length); 
    this.set_selection(start_pos,end_pos); 
    return {start: start_pos, end: end_pos, length: replace_str.length, text: replace_str}; 
    }; 

    $.fn.wrap_selection = function (left_str, right_str, sel_offset, sel_length) { 
    var the_sel_text = this.get_selection().text; 
    var selection = this.replace_selection(left_str + the_sel_text + right_str); 
    if(sel_offset !== undefined && sel_length !== undefined) 
     selection = this.set_selection(selection.start + sel_offset, selection.start + sel_offset + sel_length); 
    else if(the_sel_text == '') 
     selection = this.set_selection(selection.start + left_str.length, selection.start + left_str.length); 
    return selection; 
    }; 
}(jQuery)); 

我希望有人认为它有用！