JavaScript_object basics (must-read)

I was always a little confused when writing Java before, and most of them used jQuery, but the principle is not very clear. I have been learning JavaScript in the system recently. Please point out any questions or errors, thank you.........

Basic classes of all classes in Object

var obj = new Object();

var obj = {}; //Instantiate the object

There are two types of properties for the object:

1. Use direct quantity method: object. attribute/method, this method is intuitive and easy to understand

obj.name = 'Zhang San';

obj.age = 20;

obj.sex = 'male';

obj.say = function(){

alert("hello World");

}

2. Use "[]" method: object.['Properties/Methods']. When using this method, "" or '' must be added in brackets, and the method is relatively strict.

obj['birthday'] = '1989-08-07';

Get the attribute or method of the object: object. Attribute name/method

alert(obj.name); // Zhang San

alert(obj.age); // 20

obj.say(); // hello World

delete operator deletes the object's properties or methods

delete obj.age;

delete obj.say;

alert(obj.age); //undified

alert(obj.sex); //20

obj.say(); //An error is reported, the function has been deleted

Iterate through a js object, for in statement

for(var attr in obj){

alert(attr + ":" + obj[attr]); //The key value pairs in the array will be printed in order, the main value will be obtained if the object. attribute is used to obtain undified

}

Constructor saves the creation function of the object

alert(obj.constructor);

var o = [];

alert(o.constructor);

hasOwnProperty(propertyName) is used to detect whether a given property exists in the object, returns the boolean type, which is sometimes used in the project, so please pay attention to it

var i = {};

i.sex = 'male';

alert(i.hasOwnProperty('sex')); //true

alert(i.hasOwnProperty('age')); //false

propertyIsEnumerable(propertyName) detects whether the given property can be enumerated by for in and returns boolean

alert(i.propertyIsEnumerable('age')); //false This property is not defined above

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