maxlength.js源码

 1 /*
 2   @author: Terry
 3   @params:
 4     feedback - the selector for the element that gives the user feedback. Note that this will be relative to the form the plugin is run against.
 5     hardLimit - whether to stop the user being able to keep adding characters. Defaults to true.
 6     useInput - whether to look for a hidden input named ‘maxlength‘ instead of the maxlength attribute. Defaults to false.
 7     words - limit by characters or words, set this to true to limit by words. Defaults to false.
 8   @license: 
 9   @version: 1.2
10   @changes: code tidy via Ariel Flesler and fix when pasting over limit and including \t or \n
11 */
12 
13 (function ($) {
14 
15 $.fn.maxlength = function (settings) {
16 
17     if (typeof settings == ‘string‘) {
18         settings = { feedback : settings };
19     }
20 
21     settings = $.extend({}, $.fn.maxlength.defaults, settings);
22 
23     function length(el) {
24         var parts = el.value;
25         if ( settings.words )
26             parts = el.value.length ? parts.split(/\s+/) : { length : 0 };
27         return parts.length;
28     }
29     
30     return this.each(function () {
31         var field = this;
32         var    $field = $(field);
33         var $form = $(field.form);
34         var    limit = settings.useInput ? $form.find(‘input[name=maxlength]‘).val() : $field.attr(‘maxlength‘);
35         var    $charsLeft = $form.find(settings.feedback);
36 
37         function limitCheck(event) {
38             var len = length(this);
39             var exceeded = len >= limit;
40             var code = event.keyCode;
41             if (!exceeded )
42                 return;
43 
44                 switch (code) {
45                     case 8:  // allow delete  BackSpace BackSpace 
46                     case 9:  // Tab Tab
47                     case 17: // Next 
48                     case 36: // Home
49                     case 35: // End
50                     case 37: //
51                     case 38: //Up Arrow
52                     case 39: //Right Arrow
53                     case 40: //Dw Arrow
54                     case 46: //~
55                     case 65: //A
56                         return;
57 
58                     default:
59                         return settings.words && code != 32 && code != 13 && len == limit;
60                 }
61         }
62 
63 
64         var updateCount = function () {
65             var len = length(field);
66             var diff = limit - len;
67 
68             $charsLeft.html( diff || "0" );
69 
70             // truncation code
71             if (settings.hardLimit && diff < 0) {
72                 field.value = settings.words ? 
73                     // split by white space, capturing it in the result, then glue them back
74                     field.value.split(/(\s+)/, (limit*2)-1).join(‘‘) :
75                     field.value.substr(0, limit);
76 
77                 updateCount();
78             }
79         };
80         $field.keyup(updateCount).change(updateCount);
81         if (settings.hardLimit) {
82             $field.keydown(limitCheck);
83         }
84 
85         updateCount();
86     });
87 };
88 
89 $.fn.maxlength.defaults = {
90     useInput : false,
91     hardLimit : true,
92     feedback : ‘.charsLeft‘,
93     words : false
94 };
95 
96 })(jQuery);