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/ *
* Data Type JS
* - String String
* - Number value
* - Boolean Boolean value
* - null null
* - undefined undefined
* - more than five types belong to the basic data types, the value of the future we see
* if not the top five species, all objects
* - Object Object
*
*
* basic data types are single value "Hello" to true 123,
* there is no link between the value and the value.
** /
1, Introduction to Object
/ * object belongs to a composite data type, the object can be stored in a plurality of different types of data attributes.
*
* Category object:
* 1.
* - for example: the Math String Number The Boolean Function Object ....
*
* 2. host objects
* - objects provided by operating environment JS, the current situation mainly refers to the object provided by the browser
* - such as BOM (Browser) console
the DOM the Document *
*
* 3. custom object
* - an object created by the developers themselves
*
* /
2, create the object
mode 1:
/ *
* use the new keyword function call, the constructor constructor
* constructor is devoted function to create the object
* need not define a class by class, directly create objects, attributes may be dynamically added and removed
* the typeof a check object returns object
* /
var obj = new new object ();
/ *
* in a subject stored attribute value is called
* add attributes to the object
* syntax: Object attribute name = attribute value;.
* /
mode 2:
/ *
* Using object literal to create an object
* /
var obj = {};
//console.log(typeof obj); // Object
obj.name = "Monkey";
//console.log(obj.name) ;
/ *
* using object literal may create the object, object attribute specified directly
* syntax: {property name: property value, the property name: property value ....}
* object literal property name can be added quotes can not add, it is recommended not to increase
* If you want to use some special name, it must be quoted
*
* attribute names and values are a set of name-value of a group structure,
between the * name and value to use: connect, and more used between a name-value pairs, spaced
* if a property after no other properties, and do not write comma
* /
var obj2 = {
name: "pig",
Age: 13 is,
Gender: "M",
Test: { name: "Drifting"}
};
the console.log (obj2.test);
. 3, add the attribute
mode 1:
// add a name attribute in the obj
obj.name = "Monkey";
// add a gender attribute to the obj
obj.gender = "M";
// add a property to the age obj in
obj.age = 18;
/ *
* reads object attribute
* syntax: Object properties
* If the object does not attribute to read, does not complain but will return undefined
* /
//console.log(obj.gender);
//console.log(obj.hello);
embodiment 2:
/ *
. * to use a particular property name can not be used to operate the way
* need to use another way :
* syntax: Object [ "attribute name"] = attribute value
* need to read this way
*
* using [] attribute to operate this form, more flexible,
* a variable can be passed directly in [] so that the variable value is how much the property will be read
*
* /
Obj [ "123"] = 789;
obj [ "NiHao"] = "hello";
var n-= "NiHao";
//console.log(obj["123 "]);
. 4, delete, and modify attributes
/ *
* modify an object's property values
. * syntax: name = new object property value
* /
obj.name = "tom";
/ *
* deleted object's properties
* syntax:. delete object property name
* /
the delete obj.name;
5, the attribute value is another object
/ *
* attribute value
* JS object attribute value may be any data type
* or may be an object
* /
obj.test = to true;
obj.test = null;
obj.test undefined =;
// Create an object
var obj2 = new new Object ();
obj2.name = "pig";
// set the attributes of obj obj2
= obj2 obj.test;
the console.log (obj.test.name); // Pig
6, in the operator
/ *
* in operator
* - can be checked by the operator whether the object contains a specified attribute
* if returns true, did not return false
* - syntax:
* "attribute name" in the object
* /
//console.log(obj.test2);
// check whether it contains obj test2 property
//console.log("test5 " obj in); // false
//console.log("test "in obj); // to true
console.log (" name "in obj);to true //
7, the difference between the basic data types and reference data types
/ *
* basic data types
* Number The Boolean String Null Undefined
*
* reference data types
* Object
*
* the JS variables are saved to the stack memory,
* the value of the basic data types is stored directly in the memory stack,
* value between the value of an independent existence, modify a variable does not affect the other variables
*
* objects are saved to the stack memory, each create a new object, it will open up a new space in the heap,
* and is stored in the variable memory address of the object (reference object), if two variable is stored with an object reference,
* when a variable by modifying a property, the other will be affected
* /
var obj = new new Object ();
obj.name = "Monkey";
var obj2 = obj;
// modify the name attribute of obj
obj.name = "pig";
/*console.log(obj.name); pig
console.log (obj2.name); * / pig
// set obj2 is null, does not affect the obj
obj2 = null ;
/*console.log(obj);
the console.log (obj2); * / null
var C = 10;
D 10 = var;
//console.log(c == D);
OBJ3 new new Object = var ();
var OBJ4 = new new Object ();
obj3.name = "sand monk";
obj4.name = "sand monk";
/*console.log(obj3); // name obj = { " Shahe Shang}
the console.log (OBJ4); // obj {name = "sand monk}
/ *
* when comparing the value of two basic types of data, is a comparison value.
* When comparing the two and reference data types, it is more the memory address of the object,
* if two objects are exactly the same, but different addresses, it also returns false
* /
console.log (obj3 == OBJ4) ; // to false
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