全国统一服务热线:400-633-9193

JS与jQuery判断文本框还剩多少字符可以输入的方法

    网络     2018-10-06    1101


本文实例讲述了JS与jQuery判断文本框还剩多少字符可以输入的方法。分享给大家供大家参考,具体如下:

javascript部分:

1

2

3

4

5

6

7

8

9

10

11

function $(id) {

  return document.getElementById(id);

}

var maxLen=255;

function checkMaxInput(){

  if($("summary").value.length>maxLen){

    $("summary").value=$("summary").value.substring(0,maxLen);

  }else{

    $("leaves").innerHTML=maxLen-$("summary").value.length;

  }

}

HTML部分:

1

2

3

4

5

6

7

8

<tr>

 <td>摘要:</td>

 <td>

  <html:textarea property="summary" rows="5" cols="60" onkeyup="checkMaxInput()"/>

  <br>

   还可以输入<span class="red" id="leaves">255</span>个字符

  </td>

</tr>

jQuery插件textlimit实现Javascript统计和限制字符个数功能

使用jQuery插件textlimit可以实现统计和限制字符个数功能,可应用于文本框与文本区域,当输入文字时textlimit插件会及时统计当前文本框与文本区域中的字符个数,如果达到限制数则不允许输入,同时可设置字符删除速度,

使用实例

一、包含文件部分

1

2

<script type="text/javascript" src="jquery.js"></script>

<script type="text/javascript" src="textlimit.js"></script>

二、HTML部分

1

<input type="text" name="test" value="" id="test" /><span>20</span>/256

三、Javascript部分

1

2

3

4

5

<script type="text/javascript">

jQuery(document).ready(function(){

jQuery("#test").textlimit("span",256);

});

</script>

当在ID为test的文本框中输入文字时,textlimit插件统计当前输入字符个数并显示在一个span的元素中,如上效果图,textlimit接口如下:

1

textlimit(counter_el, thelimit, speed)

接口参数说明:

  • counter_el表示显示当前统计个数的选择器标签,如:span

  • thelimit表示限制个数,也就是最多可输入的个数,如:256

  • speed表示删除字符速度,默认为15,注意,如果不需要可设置为-1,但不能是0

注意:英文字符与汉字字符都统计为一个字符

textlimit插件统计和限制字符数非常简单,具体大家可以看看textlimit的库文件,非常值得推荐。

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

/*

 * TextLimit - jQuery plugin for counting and limiting characters for input and textarea fields

 *

 * pass '-1' as speed if you don't want the char-deletion effect. (don't just put 0)

 * Example: jQuery("Textarea").textlimit('span.counter',256)

 *

 * $Version: 2009.07.25 +r2

 * Copyright (c) 2009 Yair Even-Or

 * vsync.design@gmail.com

*/

(function(jQuery) {

  jQuery.fn.textlimit=function(counter_el, thelimit, speed) {

    var charDelSpeed = speed || 15;

    var toggleCharDel = speed != -1;

    var toggleTrim = true;

    var that = this[0];

    var isCtrl = false;

    updateCounter();

    function updateCounter(){

      if(typeof that == "object")

        jQuery(counter_el).text(thelimit - that.value.length+" characters remaining");

    };

    this.keydown (function(e){

      if(e.which == 17) isCtrl = true;

      var ctrl_a = (e.which == 65 && isCtrl == true) ? true : false; // detect and allow CTRL + A selects all.

      var ctrl_v = (e.which == 86 && isCtrl == true) ? true : false; // detect and allow CTRL + V paste.

      // 8 is 'backspace' and 46 is 'delete'

      if( this.value.length >= thelimit && e.which != '8' && e.which != '46' && ctrl_a == false && ctrl_v == false)

        e.preventDefault();

    })

    .keyup (function(e){

      updateCounter();

      if(e.which == 17)

        isCtrl=false;

      if( this.value.length >= thelimit && toggleTrim ){

        if(toggleCharDel){

          // first, trim the text a bit so the char trimming won't take forever

          // Also check if there are more than 10 extra chars, then trim. just in case.

          if ( (this.value.length - thelimit) > 10 )

            that.value = that.value.substr(0,thelimit+100);

          var init = setInterval

            (

              function(){

                if( that.value.length <= thelimit ){

                  init = clearInterval(init); updateCounter()

                }

                else{

                  // deleting extra chars (one by one)

                  that.value = that.value.substring(0,that.value.length-1); jQuery(counter_el).text('Trimming... '+(thelimit - that.value.length));

                }

              } ,charDelSpeed

            );

        }

        else this.value = that.value.substr(0,thelimit);

      }

    });

  };

})(jQuery);



  分享到:  
0.3394s