Javascript:如何从多行内容可编辑div的开头获取插入符偏移量

Question

我在使用 Javascript 从内容可编辑 div 的开头获取插入符号位置时遇到问题。我能够从 --beginning of the line-- 但不是从 div 的开头获得偏移量。从 div 开始的偏移量是我想要的。例如:

This is line number one.
This []is line number two.  <-- [] Denotes where the caret position is

当试图从 div 的 --beginning 找到插入符号位置时，我得到的值是 6，而我真的想要 30。这是我正在使用的代码:

function updateCursorPosition() {
            cursorPosition = window.getSelection().baseOffset;
            alert(cursorPosition);
        }

此函数由 onclick 事件触发。如前所述，我只是从行的开头而不是 div 的开头获取偏移量。提前感谢任何人的输入。

我正在寻找的偏移量以字符为单位，而不是以像素为单位。

Answer 1

试试下面的函数:

JSFiddle 上的示例:http://jsfiddle.net/9ThVr/

var getCaretPixelPos = function ($node, offsetx, offsety){
    offsetx = offsetx || 0;
    offsety = offsety || 0;

    var nodeLeft = 0,
        nodeTop = 0;
    if ($node){
        nodeLeft = $node.offsetLeft;
        nodeTop = $node.offsetTop;
    }

    var pos = {left: 0, top: 0};

    if (document.selection){
        var range = document.selection.createRange();
        pos.left = range.offsetLeft + offsetx - nodeLeft + 'px';
        pos.top = range.offsetTop + offsety - nodeTop + 'px';
    }else if (window.getSelection){
        var sel = window.getSelection();
        var range = sel.getRangeAt(0).cloneRange();
        try{
            range.setStart(range.startContainer, range.startOffset-1);
        }catch(e){}
        var rect = range.getBoundingClientRect();
        if (range.endOffset == 0 || range.toString() === ''){
            // first char of line
            if (range.startContainer == $node){
                // empty div
                if (range.endOffset == 0){
                    pos.top = '0px';
                    pos.left = '0px';
                }else{
                    // firefox need this
                    var range2 = range.cloneRange();
                    range2.setStart(range2.startContainer, 0);
                    var rect2 = range2.getBoundingClientRect();
                    pos.left = rect2.left + offsetx - nodeLeft + 'px';
                    pos.top = rect2.top + rect2.height + offsety - nodeTop + 'px';
                }
            }else{
                pos.top = range.startContainer.offsetTop+'px';
                pos.left = range.startContainer.offsetLeft+'px';
            }
        }else{
            pos.left = rect.left + rect.width + offsetx - nodeLeft + 'px';
            pos.top = rect.top + offsety - nodeTop + 'px';
        }
    }
    return pos;
};

以下函数可能会有所帮助。它将为您提供从文本区域开头开始和结束的选定字符。如果没有选择，它会给你插入符号的字符位置:

function getInputSelection(el) {
    var start = 0, end = 0, normalizedValue, range,
        textInputRange, len, endRange;

    if (typeof el.selectionStart == "number" && typeof el.selectionEnd == "number") {
        start = el.selectionStart;
        end = el.selectionEnd;
    } else {
        range = document.selection.createRange();

        if (range && range.parentElement() == el) {
            len = el.value.length;
            normalizedValue = el.value.replace(/\r\n/g, "\n");

            // Create a working TextRange that lives only in the input
            textInputRange = el.createTextRange();
            textInputRange.moveToBookmark(range.getBookmark());

            // Check if the start and end of the selection are at the very end
            // of the input, since moveStart/moveEnd doesn't return what we want
            // in those cases
            endRange = el.createTextRange();
            endRange.collapse(false);

            if (textInputRange.compareEndPoints("StartToEnd", endRange) > -1) {
                start = end = len;
            } else {
                start = -textInputRange.moveStart("character", -len);
                start += normalizedValue.slice(0, start).split("\n").length - 1;

                if (textInputRange.compareEndPoints("EndToEnd", endRange) > -1) {
                    end = len;
                } else {
                    end = -textInputRange.moveEnd("character", -len);
                    end += normalizedValue.slice(0, end).split("\n").length - 1;
                }
            }
        }
    }

    return {
        start: start,
        end: end
    };
}

使用示例:

var selection = getInputSelection(textarea);
var start = selection.start;
var end = selection.end;