js闭包，匿名函数概念

var functionName = function(arg){

　　//函数体

};

    function comparison(propertyName){
        return function(object1,object2){
            var value1 = object1[propertyName];
            var value2 = object2[propertyName];
            if(value1>value2){
                return -1;
            }else if(value1>value2){
                return 1;
            }else{
                return 0;
            }
        };
    }