Презентация на тему Understanding JavaScript and Coding Essentials

Types
Type Casting
Functions in JS
Input and Output
JS Code Processing
Declaration

most commonly used as part of web browsers, whose

 

3. External file:



How to add JavaScript

will be ignored by language interpreter

The /* characters, followed by

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and whose associated value may be changed.
Declaration – process

A process in which a variable is set to its first value is called initialization.

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of variables
In JavaScript

var variable; //declaration
variable =

Or quickly

var variable = 10;

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global - exist in memory and is available at

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– scalar type for integer and real digits
Boolean

var n = Number(10);
//number values for example: -1,

var s = “text”; or var s = String(“text”);
//string values for example: “”, “text”, ‘text’

var b = true; or var b = Boolean(true);
//bollean values: true and false

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can have only null value
var u;
// created and

And Object type… but it will be reviewed in future :)

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b = true;
c = a + b;

var a,

There are two types of casting:

Implicit

Explicit

But both ways given c =11 as a result!

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to convert itself to largest scalar type: Boolean to

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a set of inputs and a set of permissible

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y = f(x)

Function is a named part of a code that performs a distinct service.

= 2; result = 1;

for(i = 0; i

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a + b;
}
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* you can return one value

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( ) – operator for this action.

Usually function

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pow (base, power) {
var result = 1;

a = 30;
var b = 40;
}
var

a = 30;
var b = 40;
}
var

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a = 30;
var b = 40;
}
var

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3.

a = 30;
var b = 40;
}
var

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3.

4.

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6.

a = 30;
var b = 40;
}
var

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5.

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5.1

5.2

body;
}
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var name = function () {

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a result, functions are accessible by reference.

Functions can be

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order: from top to bottom and from left to

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of algorithms have situation when next step related of

if (condition) {
true branch;
} else {
false branch;
}

if (condition) {
true branch;
}

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(type === “silver”) {
price *=

Function get a parameter with a information about discount. And if discount is "silver" or "gold“, function modifies global variable price.

In this example a shortened form of operator was used.

to initialize a variable modifying it by simple conditions;

result = (condition)? true action: false action;

Let’s rewrite the last example using ternary operator.

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=== “silver”) {
price *= 0.9;

function discount (type) {
price *= (type === “silver”)? 0.9: 1;
price *= (type === “gold”)? 0.85: 1;

return price;
}

We get a more compact but a less readable code. So be careful!

of statements.

First of them: for - loop with counter

for

One processing of loop’s body is called iteration.

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while and do-while


while (condition) {
body of

do {
body of loop;
} while (condition);

The main difference between these loops is the moment of condition calculation. While calculates condition, and if the result is true, while does iteration. Do-while initially does iteration and after that calculates a condition.

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i < 5; i++) {
console.log(“Iteration # %d”,

Text with number of current iteration will be print 5 times

Example 2:

while (accumulation < 100) {
accumulation += doSomething();
}

This loop will be repeated until accumulation reaches 100 or gets grater value.

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for loops control :
break – aborts loop and moves

blocks of code to be executed. If all options

switch (statement) {
case value1: some body;
break;
case value2: some body;
break;
. . .
default: some body;
}

for a mark in the 5-point system

Default statement is

switch (mark) {
case 5: result = “excellent”;
break;
case 4: result = “good”;
break;
case 3: result = “satisfactorily”;
break;
case 2: result = “bad”;
break;
}