"JS Advanced Program Design" of the second

1, JS basic data type has number, String, number, Null, Undefined, Boolean, there is a complex data type Object,function and array is a derived type of object.

2, typeof used to determine the data type of a given variable,

"Undefined"-this value is undefined

"Boolean"-This value is a Boolean value

"String"-this value is a string

"Number"--this value is numeric

"Object"--this value is an object or null

"Function"-this value is

"NULL"--empty object

3, numeric conversion, number (), parseint (), parsefloat ()

4. Convert to String, toString ().

5. Properties of type Object:

Property	Meaning
Constructor	A function to create the current object is saved
hasOwnProperty (PropertyName)	Used to check whether a given property exists in the current object instance
isPrototypeOf (object)	Used to check if an incoming object is a prototype of another object
propertyIsEnumerable (PropertyName)	Used to check whether a given property can use the For-in statement to enumerate
toLocaleString ()	Returns a string representation of the object that corresponds to the region of the execution environment
ToString ()	Returns the string representation of an object
ValueOf ()	Returns a string, numeric, or Boolean representation of an object

6, Logic and (&&) and logic or (| | ) is the short-circuit operator, the former if the first is false, then the second judgment will not be made; If the first one is true, then the second one will not be judged.

7, a value and a string to add, the result is a string, 5+ "5", the result is 55.

8. Equality operator (= = =), returns true only if the two operands are equal without conversion.

The non-congruent operator (!==) returns true only if the two operands are not equal without conversion.

Null = = Undefined, the result is true, but null = = = undefined and the result is false.

9, for-in statement, is an accurate iteration of the statement, can be used to enumerate the properties of the object.

　　

 for inch expression) Statement For example: for(var in window) {   document.write (propname)  ;}

"JS Advanced Program Design" of the second