1. toString.call()
- 字符串: [object String]
- 数字: [object Number]
- 数组: [object Array]
- 对象: [object Object]
- 方法: [object Function]
- null, undefined: [object Null], [object Undefined]
- toString.call(new Date()): [object Date]
2. 判断类型：
var isArrayLike = function(collection) {
var length = getLength(collection);
return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
};
var isString = function(obj) {
return toString.call(obj) === '[object String]';
};
var isArguments = function(obj) {
return toString.call(obj) === '[object Arguments]';
};
var isArray = nativeIsArray || function(obj) {
return toString.call(obj) === '[object Array]';
};
// Is a given variable an object?
var isObject = function(obj) {
var type = typeof obj;
return type === 'function' || type === 'object' && !!obj;
};
// Is a given value a boolean?
var isBoolean = function(obj) {
return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
};
// Is a given value equal to null?
var isNull = function(obj) {
return obj === null;
};
// Is a given variable undefined?
var isUndefined = function(obj) {
return obj === void 0;
};
// Is a given array, string, or object empty?
// An "empty" object has no enumerable own-properties.
var isEmpty = function(objOrArray) {
if (objOrArray == null) {
return true;
}
if (isArrayLike(objOrArray) && (isArray(objOrArray) || isString(objOrArray) || isArguments(objOrArray))) {
return objOrArray.length === 0;
}
return keys(objOrArray).length === 0;
};
