JavaScript中的isXX系列是否继续使用的分析

isNull: function(a){
return a === null;
},
isUndefined: function(a){
return a === undefined;
},
isNumber: function(a){
return typeof a === 'number';
},
isString: function(a){
return typeof a === 'string';
},
isBoolean: function(a){
return typeof a === 'boolean';
},
isPrimitive: function(b){
var a = typeof b;
return !!(b === undefined || b === null || a == 'boolean' || a == 'number' || a == 'string');
},
isArray: function(a){
return proto_obj.toString.call(a) === '[object Array]';
},
isFunction: function(a){
return proto_obj.toString.call(a) === '[object Function]';
},
isPlainObject: function(o){
if (!o || o === win || o === doc || o === doc.body) {
return false;
}
return 'isPrototypeOf' in o && proto_obj.toString.call(o) === '[object Object]';
},
isWindow: function(o){
return o && typeof o === 'object' && 'setInterval' in o;
},
isEmptyObject: function(o){
for(var a in o) {
return false;
}
return true;
}