Cheat Sheet: Working with Objects

checkSheet.js

Cheat Sheet: Working with Objects
This section is a quick reference with pointers to more thorough explanations.
• Object literals (see “Object Literals” on page 198):

  var jane = {
    name: 'Jane',
    'not an identifier': 123,
    describe: function () { // method
      return 'Person named '+this.name;
    },
  };

  
// Call a method:
console.log(jane.describe()); // Person named Jane
• Dot operator (.) (see “Dot Operator (.): Accessing Properties via Fixed Keys” on
page 199):
obj.propKey
obj.propKey = value
delete obj.propKey


• Bracket operator ([]) (see “Bracket Operator ([]): Accessing Properties via Computed
Keys” on page 202):
obj['propKey']
obj['propKey'] = value
delete obj['propKey']


• Getting and setting the prototype (see “Getting and Setting the Prototype” on page
214):
Object.create(proto, propDescObj?)
Object.getPrototypeOf(obj)


• Iteration and detection of properties (see “Iteration and Detection of Properties”
on page 217):
Object.keys(obj)
Object.getOwnPropertyNames(obj)
Object.prototype.hasOwnProperty.call(obj, propKey)
propKey in obj


• Getting and defining properties via descriptors (see “Getting and Defining Properties
via Descriptors” on page 224):
Object.defineProperty(obj, propKey, propDesc)
Object.defineProperties(obj, propDescObj)
Object.getOwnPropertyDescriptor(obj, propKey)
Object.create(proto, propDescObj?)


• Protecting objects (see “Protecting Objects” on page 229):
Object.preventExtensions(obj)
Object.isExtensible(obj)
Object.seal(obj)
Object.isSealed(obj)
Object.freeze(obj)
Object.isFrozen(obj)


• Methods of all objects (see “Methods of All Objects” on page 257):
Object.prototype.toString()
Object.prototype.valueOf()
Object.prototype.toLocaleString()
Object.prototype.isPrototypeOf(obj)
Object.prototype.hasOwnProperty(key)
Object.prototype.propertyIsEnumerable(propKey)