通过javascript在光标处插入文本_javascript教程教程_H5之家

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>Insert Text into TextBox at Cursor Position by Javascript</title>
    <script type="text/javascript">
    var cursPos; // 窗口全局变量，保存目标 TextBox 的最后一次活动光标位置
    function insertText() {
        var txt1 = document.getElementById("Text1");
        var txt2 = document.getElementById("Text2");
        //debugger;
        if(!cursPos) TraceCursorPosition(txt2); // 获取光标位置
        txt2.value = txt2.value.slice(0, cursPos.start) +
            txt1.value + txt2.value.slice(cursPos.end)
    }

    // 跟踪光标位置
    function TraceCursorPosition(obj)
    {
        //debugger;
        cursPos = $CursorPosition(obj);
    }

    // 返回光标所在位置
    /**//*
     * source:
     * source:
     * acknowledges for Marshall
     * example:
     * var myTextBox = document.getElementById("MyTextBoxID");
     * var cursPos = $CursorPosition(myTextBox);
     * alert(cursPos.item[0] + " " + cursPos.item[1]);
     * // OR
     * alert(cursPos.start + " " + cursPos.end);
    */
    function $CursorPosition(textBox){
        var start = 0, end = 0;
        //如果是Firefox(1.5)的话，方法很简单
        if(typeof(textBox.selectionStart) == "number"){
            start = textBox.selectionStart;
            end = textBox.selectionEnd;
        }
        //下面是IE(6.0)的方法，麻烦得很，还要计算上'\n'
        else if(document.selection) {
            var range = document.selection.createRange();
            if(range.parentElement().id == textBox.id) {
                // create a selection of the whole textarea
                var range_all = document.body.createTextRange();
                range_all.moveToElementText(textBox);
                //两个range，一个是已经选择的text(range)，一个是整个textarea(range_all)
                //range_all.compareEndPoints()比较两个端点，如果range_all比range更往左(further to the left)，则
                //返回小于0的值，则range_all往右移一点，直到两个range的start相同。
                // calculate selection start point by moving beginning of range_all to beginning of range
                for (start=0; range_all.compareEndPoints("StartToStart", range) < 0; start++)
                    range_all.moveStart('character', 1);
                // get number of line breaks from textarea start to selection start and add them to start
                // 计算一下\n
                for (var i = 0; i <= start; i ++) {
                    if (textBox.value.charAt(i) == '\n')
                        start++;
                }
                // create a selection of the whole textarea
                var range_all = document.body.createTextRange();
                range_all.moveToElementText(textBox);
                // calculate selection end point by moving beginning of range_all to end of range
                for (end = 0; range_all.compareEndPoints('StartToEnd', range) < 0; end ++) {
                    range_all.moveStart('character', 1);
                }
                // get number of line breaks from textarea start to selection end and add them to end
                for (var i = 0; i <= end; i ++) {
                    if (textBox.value.charAt(i) == '\n')
                        end ++;
                }
            }
        }
        //return [start, end]; // 包括选中区域的起始位置
        // modified to return as Object
        return {"start": start, "end": end, "item": [start, end]};
    }
    </script>
</head>
<body>
    input :<input type="text" /><input type="button" value="Insert" /><br />
    output:<textarea cols="40" rows="10" onkeydown="TraceCursorPosition(this)" onkeypress="TraceCursorPosition(this)" onfocus="TraceCursorPosition(this)" onselect="TraceCursorPosition(this)" onmousedown="TraceCursorPosition(this)">hello world!</textarea><br />

</body>
</html>