A statement object

  • let obj = { 'name': 'frank', 'age': 18 }
  • let obj = new Object({'name': 'frank'})
  • console.log({ 'name': 'frank', 'age': 18 })

The key name is a string, not an identifier, and can contain any character. Quotation marks can be omitted, and only identifiers can be written after the omission. Keys (obj) can be used to obtain all keys of obj

Results obtained without quotation marks may not be as expected

let obj = {
  1: 'a'.3.2: 'b'.1e2: true.1e-2: true.234.: true.0xFF: true
};
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Object. Keys (obj) will get [” 1 “, “100”, “255”, “3.2”, “0.01”, “0.234”]

Variable and attribute names

Key is the attribute name of the object and value is the attribute value of the object

let p1 = 'name'
let obj = { p1 : 'frank'} // Write it like this, property name is 'p1'
let obj = { [p1] : 'frank' } // The property name is 'name'
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Attribute names without [] are automatically changed to strings, and attribute names with [] are evaluated as variables

var obj = {
  [1+2+3+4] :"10";
}
// keys(obj) get ["10"]
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Let a = symbol (); let obj = { [a]: ‘Hello’ };

Delete the properties

  • delete obj.xxx; 或 delete obj['xxx'];Delete XXX from objattributeThe XXX attribute is not in obj
  • obj.xxx === undefined;Delete obj from XXXAttribute values
  • available'xxx' in obj;To confirm this fact

Read properties (view all properties)

  • View all of its propertiesObject.keys(obj); Object.values(obj);Check its own value,Object.entries(obj);View their own key-value pairs
  • View self + Common propertiesconsole.dir(obj);Direct printing:obj.__proto__;(The hidden attribute has no specified name, so the latter method is not recommended)
  • Determine whether the attribute is self-contained or commonobj.hasOwnProperty('toString');

View the properties

  • obj['key']; This is recommended because the dot syntax can trick people into thinking key is not a string
  • obj.key;
  • Cheat grammar:obj[key];The value of the key variable is usually not ‘key’.

Write attributes (modify or add attributes)

  • let obj = {name: 'frank'}; // Name is a string
  • obj.name = 'frank'; // Name is a string
  • obj['name'] = 'frank';
  • obj['na'+'me'] = 'frank';
  • let key = 'name'; obj[key] = 'frank';
  • Batch assignmentObject.assign(obj, {age: 18, gender: 'man'});
  • Modify or add a common property
    • Common attributes cannot be modified or added by themselvesLet obj = {}, obj2 = {} // toString; obj.toString = 'xxx'; // Only obj attributes will be changed obj2.toString; // The toString of the prototype
    • Modify or Add attributes to the prototype In general, do not modify the prototype, it can cause a lot of problems

      • obj.__proto__.toString = 'xxx' ; // __proto__ is not recommended

      • Object.prototype.toString = 'xxx';

      • let common = {kind: 'human'};
let obj = Object.create(common);
obj.name = 'frank';
let obj2 = Object.create(common);
obj2.name = 'jack';
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        Declare obj and obj2 with common as the prototype