Functions - Reading Assignment

Javascript Programming
#262

  1. How can you create a function in Javascript?
    function(nameof thefunction){
    write here your code
    }

  2. What is the difference between var and let in regards to scope?
    a var can declared which can be used in your whole program.
    a let can be declared for just several functions
    got todo with scope.

  3. What is a pure function?
    A function with no side effects

#263
  1. How can you create a function in Javascript?

By creating a value first from which we are creating a function using const or let:

const square = function(x) {
    return x * x;
};

Or by declaring a function:

function square(x) {
    return x * x;
}
  1. What is the difference between var and let in regards to scope?

Var is working in the scope of function and let/const are working in the scope of block.

What means that, if we use var in the function and within that function we will naste another function with the same variable, it will overwrite our var for the whole function.

function testVar() {
    var x = 10;
    console.log(x); // 10
    if (true) {
        var x = 20;
        console.log(x); // 20
    }
    console.log(x); // 20
}

On the other hand, when we use let/const in the function and within that function we will naste another function with the same variable, it will stay only in that nasted function and when the nasted function will end executing its code, we will come back to first value for our binding.

function testVar() {
    var x = 10;
    console.log(x); // 10
    if (true) {
        let x = 20;
        console.log(x); // 20
    }
    console.log(x); // 10
}
  1. What is a pure function?

A function is only pure if, given the same input, it will always produce the same output and doesn’t produce ant side fx.

function pure(arg) {
    return arg * 4
}

/* Note that a parameter is a named variable passed into a function 
whereas, an arguments are the data which you pass into parameters 
when method is called.*/

function f(a){ => // a is a parameter
}

f(5) => //5 is an argument.

It is based on the input, it will always give the same output fir the given input and it doesn’t affect any external code.

PS: I don’t understand problem with var and let. When I used to learning to program in Java it was obvious for me that, when I updated a variable in a function it was with purpose, like in this example (I guess at least):

public static void testVar() {
     int x = 10;
     System.out.println(x); // 10
     if (true){
         x = 20;
         System.out.println(x); // 20
     }
     System.out.println(x); // 20
}

For sure with experience I will get it why it is good to use let, because my WebStorm also encourage me to use let instead var. @ivan

#264
  1. With word functions then (input parameters) then {some code;} and bind it to a name:
    let myFunc = function(a, b){some code;}; or function myFunc(a, b) {some code;}
  2. var can be visible outside of its scope, let can be visible only within its scope
  3. Pure function does not produce side effects and does not rely on any variables that are declared outside of it
#265

How can you create a function in Javascript?

Through using the function keyword as an expression we can create a function value. Or function can be used to create a binding and assign a value. The final way to create a function is to use => this is the same as calling the term function, but is less verbose.

What is the difference between var and let in regards to scope?

Var allows for a greater scope in that a binding created with var will be seen throughout a function. Let creates a narrow scope in that only that function will be able to see it; in other words, if there is a nested function within another function and you bind a statement with let, only that inner function will ‘see’ it.

What is a pure function?

A pure function is a specific kind of value-producing function that not only has no side effects but also doesn’t rely on side effects from other code.

#266
  1. You can define the function:

const fairy = function() {
console.log(“tail”);
};

You can declare the function:

function multiply(a, b) {
return a * b;
}

Or, you can use arrow notation:

var add = x => x + x;

  1. The keyword let is only visible within the local scope of the function in which it is defined. It will not be “seen”, or defined, outside of the function environment. However, the keyword var can be seen on a global scope even when it is defined within a function. It will fall under the global scope or the nearest function scope.

  2. A pure function is a function with no side effects that is not influenced by any other global bindings.

#267

  1. How can you create a function in Javascript?
    A function is created with an expression, that starts with the keyword “function”, following by parameters in() and the body in{}.
    e.g.: const MyName=function(Name,Surname){code}
    function MyName(Name,Surname){code}

  2. What is the difference between var and let in regards to scope? The main difference is that “var” is visible throughout the whole function, so the whole program after the declaration can see it, whereas “let” is visible only inside the loop and it´s not visible after the loop.

  3. What is a pure function?
    A pure function doesn´t produce side-effects and also doesn´t rely on side effects from other code. It always produce the same value, if called with the same arguments.

#268
  1. How can you create a function in Javascript?

A function consists of a regular binding where the value of the binding is a function.

You create a function by starting with the word function that expresses a set of parameters () and a body – the body must always be wrapped in braces {}.

  1. What is the difference between var and let in regards to scope?

Bindings, created with the var keyword, are visible throughout the whole function that they appear in—or throughout the global scope, if they are not in a function. Let can be visible only within its scope of its function.

  1. What is a pure function?

A pure function is a specific kind of value-producing function that not only has no side effects but also doesn’t rely on side effects from other code

#269
  1. “A function is created with an expression that starts with the keyword function.”
  2. Bindings declared with let are local to the block that they are declared in whereas var are in the nearest function scope or the global scope.
  3. A function that does not produce side effects nor rely on side effects from other code.
#270
  1. How can you create a function in Javascript?
    function()
  2. What is the difference between var and let in regards to scope?
    var is accessible throughout the program while let is local to the code block
  3. What is a pure function?
    A pure function is a specific kind of value-producing function that not only
    has no side effects but also doesn’t rely on side effects from other code. A pure
    function has the pleasant property that, when called with the same arguments,
    it always produces the same value (and doesn’t do anything else).
#271
  1. How can you create a function in Javascript?

A function expression in JavaScript is defined: function funtionName (Argument1, Argument2, …) {

set of instructions and even functions

}

function(param1, param2) {

// do something meaningful here…

}

The function can be given a name ( function definition ) by simply assigning the function expression to a binding, e.g.:

const add = function(x, y) { return x + y; };

Ex. function Using prompt alert to show a pop up to the user, this uses a predetermined function to make it show up.

  1. What is the difference between var and let in regards to scope?

Bindings declared with let (and const ) are local to the block they are declared in, while var bindings are visible in the whole function they are declared in (or global, if they aren’t in any function). So a var remains throughout the whole program and let can be used to insert another value instead of var for the same parameter. Const can`t be changed.

  1. What is a pure function?

A pure function is a function that doesn’t have any side-effects and doesn’t rely on side-effects from other code. It has the property that it always produces the same value if the same inputs are passed.

#272
  1. By typing function a() { }.
  2. var is global and is seen throughout whole function global, let is more local and usually seen in its block.
  3. Pure functions are function that accept an input and returns a value without modifying any data outside its scope.
#273

How can you create a function in Javascript?
-You express the function name and write the parameters inside brackets.
Then you make the body which contains statements to be executed when function is called.

What is the difference between var and let in regards to scope?
-let works inde a block. If you make one inside of a loop the code
before or after it can not “see” it. bindings made with var are visible
throughout the whole function or global scope

What is a pure function?
-It has no side effects and does not rely on side effects from other code(doesn’t read global bindings).
It always produces the same value.

#274

  1. How can you create a function in Javascript?
    -> A function is created with an expression that starts with the keyword function. Functions have a set of parameters (in this case, only x) and a body, which contains the statements that are to be executed when the function is called. The function body of a function created this way must always be wrapped in braces, even when it consists of only a single statement.

  2. What is the difference between var and let in regards to scope?
    -> Bindings declared with let are in fact local to the block that they are declared in. Functions created with the var keyword, are visible throughout the whole function that they appear in—or throughout the global scope, if they are not in a function.

  3. What is a pure function?
    -> A pure function is a specific kind of value-producing function that not only
    has no side effects but also doesn’t rely on side effects from other code—for
    example, it doesn’t read global bindings whose value might change. A pure
    function has the pleasant property that, when called with the same arguments,
    it always produces the same value (and doesn’t do anything else).

#275

How can you create a function in Javascript?
A function is created by defining a variable then the function parameters
const [Variable] = function([Object]){[Function Parameters]}

What is the difference between var and let in regards to scope?
variables defined with “let” (or const) are “…local to the block that they
are declared in…”
variables defined with “var” “…are visible
throughout the whole function that they appear in—or throughout the global
scope…”

What is a pure function?
“A pure function is a specific kind of value-producing function that not only
has no side effects but also doesn’t rely on side effects from other code…”
For this reason pure functions can reliably produce the same output when given the same input (regardless of how the code outside the function is changed.

#276

  1. a) Expression: const f = function(x) { return x+x; };
    b) statement: function g () = { return ‘hello’; };
    c) arrow: const h = x => x * 5;

  2. each loop and function forms its own scope in which local variables can be defined and used.
    “var” is obsolete and does not know the loopscope -> so it is also valid outside the loop. For functions var is only valid within the scope.

  3. a pure function has no side effects and didn’t use any global variable.It is a “stand alone” function

#277

  1. You crate a function with an expression that starts with the keyword function.

  2. The difference is that when var is declared it is viewed as a global scope while let is viewed as a local scope.

  3. A pure function is a specific kind value producing function that not only has no side effects from code.

#278

  1. By creating an expression with the keyword “function”. It has a set of parameters, and a body which contains the statements to be executed.

  2. A binding declared with “let” is only visible within the block in which is declared. A binding declared with “var” is visible within that block and outside it.

  3. A pure function is a function that does not produce side effects. It also does not rely on side effects from other code.

#279

image How can you create a function in Javascript? A function is created with an expression that starts with the keyword function. Functions have a set of parameters and a body, which
contains the statements that are to be executed when the function is called.
The function body of a function created this way must always be wrapped in braces, even when it consists of only a single statement.
What is the difference between var and let in regards to scope? Bindings declared with let which are local to the block that they are declared inside of a loop, the code before and after the loop cannot “see” it.
Var keyword, are visible throughout the whole function that they appear in—or throughout the global scope, if they are not in a function.
What is a pure function? A pure function is a specific kind of value-producing function that not only has no side effects but also doesn’t rely on side effects from other code—for example, it doesn’t read global bindings whose value might change.

#280

1.A function is JavaScript vocabulary that is created by typing in a valid word to produce a value

2.var assigns a binding that is global to the scope of the programme, while let is local

3.A pure function is one which has no side effects, not rely on global bindings

#281
  1. function nameOfFunction (Parameter1, Parameter2, etc) {instructions}
  2. let has a local scope and can not be called outside the block it has been used in, var has global purpose and can be called if outside the block as well when declared outside that block.
  3. A ‘pure function’ is a function that does not create any side effects and doesn’t rely on side-effects from other code. It produces the same value if the same inputs are used.