Fungsi kursor 6 jQuery

// jQuery 获取光标位置函数调用示例
$("input[name='username']").getCursorPosition();

jQuery.fn.getCursorPosition = function(){
    if(this.length == 0) return -1;
    return $(this).getSelectionStart();
};

// jQuery 设置光标位置函数调用示例
$("input[name='username']").setCursorPosition(5);

jQuery.fn.setCursorPosition = function(position){
    if(this.length == 0) return this;
    return $(this).setSelection(position, position);
};

// jQuery 获取文本选择函数调用示例
$("input[name='username']").getSelection();

jQuery.fn.getSelection = function(){
    if(this.length == 0) return -1;
    var s = $(this).getSelectionStart();
    var e = $(this).getSelectionEnd();
    return this[0].value.substring(s,e);
};

// jQuery 获取文本选择起始位置函数调用示例
$("input[name='username']").getSelectionStart();

jQuery.fn.getSelectionStart = function(){
    if(this.length == 0) return -1;
    var input = this[0];
    var pos = input.value.length;

    if (input.createTextRange) {
        var r = document.selection.createRange().duplicate();
        r.moveEnd('character', input.value.length);
        if (r.text == '') 
            pos = input.value.length;
        pos = input.value.lastIndexOf(r.text);
    } else if(typeof(input.selectionStart)!="undefined")
        pos = input.selectionStart;

    return pos;
};

// jQuery 获取文本选择结束位置函数调用示例
$("input[name='username']").getSelectionEnd();

jQuery.fn.getSelectionEnd = function(){
    if(this.length == 0) return -1;
    var input = this[0];
    var pos = input.value.length;

    if (input.createTextRange) {
        var r = document.selection.createRange().duplicate();
        r.moveStart('character', -input.value.length);
        if (r.text == '') 
            pos = input.value.length;
        pos = input.value.lastIndexOf(r.text);
    } else if(typeof(input.selectionEnd)!="undefined")
        pos = input.selectionEnd;

    return pos;
};

// jQuery 设置文本选择函数调用示例
$("input[name='username']").setSelection(4, 20);

jQuery.fn.setSelection = function(selectionStart, selectionEnd) {
    if(this.length == 0) return this;
    var 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;
};