Essential Books

The delete operator

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The delete operator deletes a property from an object.

Syntax: 

delete object.property

delete object['property']

Returns:

If deletion is successful, or the property did not exist:

If the property to be deleted is an own non-configurable property (can’t be deleted):

Description

The delete operator does not directly free memory. It can indirectly free memory if the operation means all references to the property are gone.

delete works on an object’s properties. If a property with the same name exists on the object’s prototype chain, the property will be inherited from the prototype.

delete does not work on variables or function names.

Examples: 

// Deleting a property
foo = 1;              // a global variable is a property of `window`: `window.foo`
delete foo;           // true
console.log(foo);     // Uncaught ReferenceError: foo is not defined

// Deleting a variable
var foo = 1;
delete foo;           // false
console.log(foo);     // 1 (Not deleted)

// Deleting a function
function foo(){ };
delete foo;           // false
console.log(foo);     // function foo(){ } (Not deleted)

// Deleting a property
var foo = { bar: "42" };
delete foo.bar;       // true
console.log(foo);     // Object { } (Deleted bar)

// Deleting a property that does not exist
var foo = { };
delete foo.bar;       // true
console.log(foo);     // Object { } (No errors, nothing deleted)

// Deleting a non-configurable property of a predefined object
delete Math.PI;       // false  ()
console.log(Math.PI); // 3.141592653589793 (Not deleted)
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Unary Operators:
* Syntax
* Overview
* The typeof operator
* The delete operator
* The unary plus operator
* The void operator
* The unary negation operator (-)
* he bitwise NOT operator
* The logical NOT operator
Table Of Contents
0 Getting started
1 Comments
2 Basic data types
3 Built-in constants
4 Variables
5 Declarations and assignments
6 Reserved keywords
7 Data types in JavaScript
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10 Template Literals
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48 Timestamps
49 Destructuring assignment
50 Web Worker
51 Debugging
52 Notifications API
53 WebSockets
54 Web Cryptography API
55 Async functions, async / await
56 Constructor functions
57 execCommand and contenteditable
58 Performance Tips
59 Design patterns
60 requestAnimationFrame
61 Method chaining
62 Global error handling in browsers
63 File API, blobs and FileReaders
64 Console
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66 Detecting browser
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69 Localization
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71 Callbacks
72 Functional JavaScript
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78 BOM Browser Object Model
79 Unit Testing
80 Linters for ensuring code quality
81 Automatic Semicolon Insertion
82 IndexedDB
83 Anti-patterns
84 Navigator Object
85 Modularization techniques
86 Proxy
87 Same origin policy, cross-origin communication
88 postMessage and MessageEvent
89 WeakMap
90 WeakSet
91 Behaviroal Design Patterns
92 Server-sent events
93 Async iterators
94 Namespacing
95 Evaluating JavaScript
96 Memory efficiency
97 How to make iterator usable inside async callback function
98 Context this
99 Setters and getters
100 Vibration API
101 Fluent API
102 Tilde
103 Security issues
104 Get and set CSS custom variables
105 Contributors