In JavaScript the execution context for an execution is by default global. That means that when this is used in a function it refers to the owner of the function, that is in the object where it exists. I JavaScript there are some differences between strict mode and non-strict mode and mostly the value of this is determined by how a function is called.
The value this cannot be set by assignment during execution and the value can be different every time the function is called.
var aThisTest = { prop: 66, func: function () { return aThisTest.prop; }, }; alert(aThisTest.func()); // Output: 66
When we are operating in a global execution context (not inside any function), this refers to the global object both in strict and none-strict.
// In a web browser the global object is the same as the window object. alert(this === window); // Result: true count = 99; alert(window.count); // Result: 99 this.testString = "Honneybag"; alert(window.testString ) // Result: "Honneybag" alert(testString ) // Result: "Honneybag"
When the value of this isn't set by the call and the code is in none-strict mode, this is by default set the global object. The global object in this context is the window in a browser.
function TestThisFunction() { return this; } TestThisFunction() === window; // true: the result in a browswer TestThisFunction() === global; // true: the result in node
When using the value of this in strict mode it stays the same as it was set to, when entering the execution context. Therefore in this example this will be undefined.
function TestThisFunction() { 'use strict'; // see strict mode return this; } TestThisFunction() === undefined; // true
There will be errors in the code. It is good practice to handle exceptions/errors.
Exceptions are a type of error that occurs during the execution of an application. Errors should be logged. Sometimes it is possible to recover a bug and proceed.
Other cases the user should get inform....
The break statement terminates a current loop or a switch statement.
The continue statement "jumps over" one iteration in the current loop.
Bitwise operators will handle their operands as a sequence of 32 bits (zeroes and ones), and not like decimal, hexadecimal, or octal numbers. For example, the decimal number nine has a binary representation of 1001. Bitwise operators perform their operation....
With operator precedence we describe the order in which operations are executed when expressions are evaluated. The operations with a higher precedence will run before the operations with a lower precedence. For example, multiplication is performed before addition.
JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:
1. HTML to define the content of web pages.
2. CSS to specify the layout of web pages.
3. JavaScript to program the behavior of web pages.
JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved. The benefits of using JavaScript are: 1. You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server. 2. Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something. 3. Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard. 4. Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.
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