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1. Top results related to what is a javascript function?

   • Javascript, what if a parameter of a function is a function?

     Top Answer

     Answered Sep 26, 2019 · 0 votes

     Just check this:

     function do2and3(operation) { console.log(operation(2, 3));}-do2and3((x, y) => x + y); // Adddo2and3((x, y) => x - y); // Reductdo2and3((x, y) => x * y); // Multiplydo2and3((x, y) => x / y); // Dividedo2and3(function(x, y) { // A more complex example console.log(x); console.log(y); return Math.pow(x, y);})

     Passing functions as parameters allow the main function to call it as if were a normal function, this give you the ability to extend something without modifying it.

     The advantage of doing this is that you can "inject" functionality to an existing function without altering it.

     Check all answers on Stack Overflow

     1/5

   • What is a Unary Function in JavaScript?

     A unary function is similar to the unary operator as the unary operator allows you to operate it with only one operand in a similar way a unary function allows you to pass only a single parameter to it. A unary function accepts only a single parameter and operates the different operations on it inside the function body. A unary function can be defined using any of the methods available in JavaScript to declare functions. The word unary means single or mono which means it can be operated with only one parameter.

     Example: The below code example will explain the concept of the unary operator in JavaScript.

     Javascript

     function unaryFunc(param){    console.log(param*33);}unaryFunc(5);unaryFunc(3);-

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     2/5

   • What is a "scoping function" in javascript?

     Top Answer

     Answered Apr 05, 2021 · 2 votes

     In JavaScript, variables declared with var

     are "function scoped" not "block scoped" like in other C-like languages (and how the {} syntax might imply). (Update Re: block scoping: ES6 introduced block scoping with two new variable declarations, let and const. See https://www.freecodecamp.org/news/var-let-and-const-whats-the-difference/)

     To create a module with a "scoping function" means to use a function to wrap the scope of variables and other logic you may use, and then return an object literal with the results you want.

     Example:

     function personFacory(name) { var person = { name: name }; if (name === 'Bob') { person.isBob = true; } return person;}

     The case of the IIFE and closure @Josh mentions is also a valuable use of a "scoping function."

     Another example:

     var generateId = (function(){ var currentId = 0; return function() { return currentId++; };})();

     Each time you call generateId(), it will return the next integer.

     Check all answers on Stack Overflow

     3/5

   • What is a First Order Function in JavaScript ?

     A First Order Function is just a normal regular function that does not take any function as one of its parameters and also it does not return another function as its return value inside its body. It is a simple function that accepts the parameters of different data types either primitive or non-primitive and it may or may not return a value as a result of the calculations performed on the passed parameters. A First Order Function can be declared using any of the methods available in JavaScript.

     Example: The below code will explain how you can declare a general first-order function in JavaScript.

     Javascript

     function firstOrderFunc(num1, num2){    console.log(num1*num2);}firstOrderFunc(4, 35)-

     Output

     140-

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     4/5

   • What is the purpose of a parameter named "undefined" in a JavaScript function?

     Top Answer

     Answered Jun 23, 2012 · 20 votes

     What this is doing, is reassigning undefined to undefined inside that closure. Thats a failsafe. Because other code may accidentally do something like

     undefined = something;console.log(undefined); // will output 'something'-

     And thats valid in javascript(if the JS engine being used has not implemented ECMAScript 5 specification, in ECMAScript 5 spec undefined is non non-writable, MDN DOC ),

     Quote from MDN New_in_JavaScript 1.8.5 (ECMA 5) Page

     Changes to global objects

     Global objects made read only

     The NaN, Infinity, and undefined global objects have been made read only, per the ECMAScript 5 specification.

     And from ES5 Annotated Spec in Guthub

     ES5 spec Section x15.1.1.3

     15.1.1.3 undefined

     The value of undefined is undefined (see 8.1).

     This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

     Even if global undefined is not writable You can have a local variable named undefined and can mess up your code(mainly comparisons with undefined). But that's your responsibility. You can have codes like

     (function(){ console.log('Second Case: '); var undefined = 'Something'; console.log(undefined); // Will log `something` var a ; // a is undefined console.log(a === undefined); // false, as undefined is changed // you might expect a === undefined will return true, but as // `undefined` is changed it will return false. console.log(a); // undefined})();

     Demo: http://jsfiddle.net/joycse06/V4DKN/

     However if undefined is writeable then the above assignment may hamper many comparison made with undefined after that line of code as undefined is not undefined anymore. It has some value now.

     So as they are calling that anonymous function like

     ( window ) // one argument only-

     And receiving

     ( window, undefined) // only window is passed when calling the function // Second argument is not passed means it's undefined // so undefined is restored to undefined inside that function // and no global accidental assignments can hamper jQuery's // code using 'undefined' now

     That means inside that closure undefined is restored to undefined, as it has not been passed any value thus securing use of undefined inside that anonymous function.

     A very good detailed article on this http://javascriptweblog.wordpress.com/2010/08/16/understanding-undefined-and-preventing-referenceerrors/

     I am quoting some lines from the above article link to make things clear

     What is undefined?

     In JavaScript there is Undefined (type), undefined (value) and undefined (variable).

     Undefined (type) is a built-in JavaScript type.

     undefined (value) is a primitive and is the sole value of the Undefined type.

     Any property that has not been assigned a value, assumes the undefined value. (ECMA 4.3.9 and 4.3.10).

     A function without a return statement, or a function with an empty return statement returns undefined. The value of an unsupplied function argument is undefined.

     var a;typeof a; //"undefined"-window.b;typeof window.b; //"undefined"var c = (function() {})();typeof c; //"undefined"var d = (function(e) {return e})();typeof d; //"undefined"

     undefined (variable) is a global property whose initial value is undefined (value), Since its a global property we can also access it as a variable. For consistency I’m always going to call it a variable in this article.

     typeof undefined; //"undefined"var f = 2;f = undefined; //re-assigning to undefined (variable)typeof f; //"undefined"

     As of ECMA 3, its value can be reassigned :

     undefined = "washing machine"; //assign a string to undefined (variable)typeof undefined //"string"f = undefined;typeof f; //"string"f; //"washing machine"

     Needless to say, re-assigning values to the undefined variable is very bad practice, and in fact its not allowed by ECMA 5.

     Check all answers on Stack Overflow

     5/5

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2. www.w3schools.com › js › js_functionsJavaScript Functions - W3Schools

   www.w3schools.com › js › js_functions

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   A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses (). Function names can contain letters, digits, underscores, and dollar signs (same rules as variables). The parentheses may include parameter names separated by commas: (parameter1, parameter2, ...) The code to be executed, by the function ...

3. developer.mozilla.org › JavaScript › GuideFunctions - JavaScript | MDN - MDN Web Docs

   developer.mozilla.org › JavaScript › Guide

   • Cached

   • Defining functions. Function declarations. A function definition (also called a function declaration, or function statement) consists of the function keyword, followed by
   • Calling functions. Defining a function does not execute it. Defining it names the function and specifies what to do when the function is called. Calling the function actually performs the specified actions with the indicated parameters.
   • Function scope. Variables defined inside a function cannot be accessed from anywhere outside the function, because the variable is defined only in the scope of the function.
   • Scope and the function stack. Recursion. A function can refer to and call itself. There are three ways for a function to refer to itself: The function's name.

4. developer.mozilla.org › Reference › FunctionsFunctions - JavaScript | MDN - MDN Web Docs

   developer.mozilla.org › Reference › Functions

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   Oct 4, 2023 · Generally speaking, a function is a "subprogram" that can be called by code external (or internal, in the case of recursion) to the function. Like the program itself, a function is composed of a sequence of statements called the function body. Values can be passed to a function as parameters, and the function will return a value.

5. People also ask

   What is a function in JavaScript?

   • Define a function which is referenced by any one of word. Normally, only one wordis provided; multiple wordsare usually only useful for setting traps. The body of the function is the listbetweenthe {and }. See Functions. The options of functionhave the following meanings: -T Enable tracing for this function, as though with functions -T.

   zsh: 6 Shell Grammar - SourceForge

   zsh.sourceforge.io/Doc/Release/Shell-Grammar.html

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   What is return in JavaScript?

   • RETURN is usually placed at the end of a program, procedure, or function to return control to a higher-level program. However, an implicit RETURN is executed if you omit RETURN. You can direct where focus is assigned using the optional oObjectNameparameter in the RETURN command of the Valid Event.

   RETURN Command - Yaldex

   www.yaldex.com/fox_pro_tutorial/html/be8039a8-8ffb-4f89-823d-e8c6a14f7dbd.htm

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   What is the difference between function statement and function expression?

   • A function expression is very similar to and has almost the same syntax as a function statement. The function statement declares function with the specified parameters. A function expression produces a value (the function). A function declaration (read: statement) leads to an action – the creation of a variable whose value is the function.

   What is the difference between function statement and function ... - Qu…

   www.quora.com/What-is-the-difference-between-function-statement-and-function-expression-in-JavaScript

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6. www.freecodecamp.org › news › what-are-functions-inWhat are Functions in JavaScript? A Beginner's Guide

   www.freecodecamp.org › news › what-are-functions-in

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   Jun 30, 2022 · ADVERTISEMENT. Functions are one of the fundamental concepts in programming. They let us write concise, modular, reusable, and maintainable code. They also help us obey the DRY principle when writing code. In this article, you will learn what functions are in JavaScript, how to write your own custom functions, and how.

7. javascript.info › function-basicsFunctions - The Modern JavaScript Tutorial

   javascript.info › function-basics

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   Oct 14, 2022 · A function can return a value back into the calling code as the result. The simplest example would be a function that sums two values: function sum(a, b) { return a + b; } let result = sum(1, 2); alert( result ); // 3. The directive return can be in any place of the function.

8. www.javascripttutorial.net › javascript-functionJavaScript Functions - JavaScript Tutorial

   www.javascripttutorial.net › javascript-function

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   function square (a) { } Code language: JavaScript (javascript) The following declares a function named add() that accepts two parameters: function add (a, b) { } Code language: JavaScript (javascript) Inside the function body, you can write the code to implement an action. For example, the following say() function simply shows a message to the ...

9. www.freecodecamp.org › news › what-is-a-functionWhat is a function in JavaScript? - freeCodeCamp.org

   www.freecodecamp.org › news › what-is-a-function

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   Sep 7, 2021 · JavaScript Function Examples. Dionysia Lemonaki. Functions are one of the main parts of computer programs. They are widely used and are one of JavaScript's fundamental building blocks. In this article, we'll go over the definition of functions and why they are so important.