监听VAL 值的变化

*下面封装的监控TEXT VAL 值 的函数*/
$.event.special.valuechange = {

    teardown: function (namespaces) {
        $(this).unbind('.valuechange');
    },

    handler: function (e) {
        $.event.special.valuechange.triggerChanged($(this));
    },

    add: function (obj) {
        $(this).on('keyup.valuechange cut.valuechange paste.valuechange input.valuechange', obj.selector, $.event.special.valuechange.handler)
    },

    triggerChanged: function (element) {
        var current = element[0].contentEditable === 'true' ? element.html() : element.val()
          , previous = typeof element.data('previous') === 'undefined' ? element[0].defaultValue : element.data('previous')
        if (current !== previous) {
            element.trigger('valuechange', [element.data('previous')])
            element.data('previous', current)
        }
    }
}

用法：

   $('.edit-word-text').on('valuechange', function (e, previous) {
            /*$('#output').append('previous: ' +  previous +  '  --  current: ' + $(this).val() + '<br />')*/
            $("#canvas").find(".page").find(".fontAtHover").html($(this).val())

        })