getSelection不适用于在input元素中选择的文本，但不适用于在页面中对元素进行的选择。

您可以使用selectionStart和selectionEnd这样的：

return document.activeElement.value.substring(
   document.activeElement.selectionStart,
   document.activeElement.selectionEnd)

您可能应该为此创建一个函数，而不是单行代码。也许您还想然后测试是否document.activeElement确实是正确的元素类型，等等。当您使用它时，您甚至可以使其与IE9之前的浏览器兼容……（[尽管很困难]

简单功能

这也将工作的input或者textarea没有重点控制：

function getInputSelection(el) {
    if (el.selectionStart !== undefined) {
        return el.value.substring(el.selectionStart, el.selectionEnd);
    }
}
// Example call:
console.log(getInputSelection(document.activeElement));

广泛的jQuery插件

这提供了更多的跨浏览器兼容性（pre-
IE9），并且不仅支持以jQuery插件的形式获取，而且还支持选择范围和文本的设置。它处理一个事实，即CRLF字符序列以一种务实的方式算作一个字符位置（LF仅在原处替换）：

/**
 * jQuery plug-in for getting/setting the selection range and text  
 *   within input/textarea element(s). When the selection is set,
 *   the element will receive focus. When getting the selection,
 *   some browsers require the element to have focus (IE8 and below).
 *   It is up to the caller to set the focus first, if so needed.
 * @this {jQuery} Input/textarea element(s).
 * @param {object} opt_bounds When provided, it sets the range as follows:
 * @param {number} opt_bounds.start Optional start of the range. If not
 *   provided, the start point of the range is not altered.
 * @param {number} opt_bounds.end Optional end of the range. If not
 *   provided, the end point of the range is not altered. If null, the end
 *   of the text value is assumed.
 * @param {number} opt_bounds.text Optional text to put in the range. If
 *   not provided, no change will be made to the range's text.
 * @return {jQuery|object|undefined} When setting: the same as @this to 
 *   allow chaining, when getting, an object {start, end, text, length} 
 *   representing the selection in the first element if that info
 *   is available, undefined otherwise.
 */
$.fn.selection = function (opt_bounds) {
    var bounds, inputRange, input, docRange, value;

    function removeCR(s) {
        // CRLF counts as one unit in text box, so replace with 1 char 
        // for correct offsetting
        return s.replace(/\r\n/g, '\n');
    }

    if (opt_bounds === undefined) {
        // Get 
        if (!this.length) {
            return;
        }
        bounds = {};
        input = this[0];
        if (input.setSelectionRange) {
            // Modern browsers
            bounds.start = input.selectionStart;
            bounds.end = input.selectionEnd;
        } else {
            // Check browser support
            if (!document.selection || !document.selection.createRange) {
                return;
            }
            // IE8 or older
            docRange = document.selection.createRange();
            // Selection must be confined to input only
            if (!docRange || docRange.parentElement() !== input) { return; }
            // Create another range that can only extend within the
            // input boundaries.
            inputRange = input.createTextRange();
            inputRange.moveToBookmark(docRange.getBookmark());
            // Measure how many characters we can go back within the input:
            bounds.start =
                -inputRange.moveStart('character', -input.value.length);
            bounds.end = -inputRange.moveEnd('character', -input.value.length);
        }
        // Add properties:
        bounds.length = bounds.end - bounds.start;
        bounds.text = removeCR(input.value).
            substr(bounds.start, bounds.length);
        return bounds;
    }
    // Set
    if (opt_bounds.text !== undefined) {
        opt_bounds.text = removeCR(opt_bounds.text);
    }
    return this.each(function () {
        bounds = $.extend($(this).selection(), opt_bounds);
        bounds.end = bounds.end === null ? this.value.length : bounds.end;
        if (opt_bounds.text !== undefined) {
            value = removeCR(this.value);
            this.value = value.substr(0, bounds.start) + bounds.text +
                value.substr(bounds.end);
            bounds.end = bounds.start + bounds.text.length;
        }
        if (this.setSelectionRange) {
            // Modern browsers
            // Call .focus() to align with IE8 behaviour.
            // You can leave that out if you don't care about that.
            this.focus();
            this.setSelectionRange(bounds.start, bounds.end);
        } else if (this.createTextRange) {
            // IE8 and before
            inputRange = this.createTextRange();
            inputRange.collapse(true);
            inputRange.moveEnd('character', bounds.end);
            inputRange.moveStart('character', bounds.start);
            // .select() will also focus the element:
            inputRange.select();
        }
    });
};

使用示例：

// Get
console.log($('textarea').selection().text);
// Set text
$('textarea').selection({text: "Hello!"});
// Set starting point of selection
$('textarea').selection({start: 1});