directive 限制输入的最大数，最小数无法设置，因为删除时无法判断

limit-max.js

var app = angular.module('limit-max', []);

/**
 * 限制输入的最大数，最小数无法设置，因为删除时无法判断
 * @example
 * <input ng-model="xx" type="number" limit-max="100">
 */
app.directive('limitMax', function() {
    return {
        restrict : 'A',
        scope: {
            ngModel: '='
        },
        link: function(scope, element, attrs) {
            var max = +attrs.limitMax;

            scope.$watch('ngModel', function(newVal, oldVal) {
                var isNumber = /^\d{1,}$/.test(newVal);

                if(!isNumber) {
                    return  scope.ngModel = null;
                }

                if(max && newVal > max) scope.ngModel = max;
            });
        }
    }
});