将鼠标焦点定位到文本框最后

经测试，兼容IE8

//设置焦点相关---begin
//用法：$("#txtInput").val("你好").focusEnd();
$.fn.setCursorPosition = function (position) {
    if (this.lengh == 0) return this;
    return $(this).setSelection(position, position);
}

$.fn.setSelection = function (selectionStart, selectionEnd) {
    if (this.lengh == 0) return this;
    input = this[0];

    if (input.createTextRange) {
        var range = input.createTextRange();
        range.collapse(true);
        range.moveEnd('character', selectionEnd);
        range.moveStart('character', selectionStart);
        range.select();
    } else if (input.setSelectionRange) {
        input.focus();
        input.setSelectionRange(selectionStart, selectionEnd);
    }

    return this;
}

$.fn.focusEnd = function () {
    if (this.val() != undefined) {
        this.setCursorPosition(this.val().length);
    }
}
//设置焦点相关---end