IT PhD Computer Journal

In JavaScript, in addition to the while and for loops, there is another variant of the do-while loop:

do{
}while();

The meaning of this construct is that what is inside the curly braces is executed first, and then the while() condition is checked. If the condition is true, then the loop is repeated, if false, then the loop ends. Thus, the loop will be executed at least once. This loop is used less frequently than the previous two because it is easier for a human to understand a regular while loop to read the condition, rather than looking for the condition at the end of the loop. Continue reading →

JavaScript has two loops, while and for. They both run at the same speed. The for loop is more flexible – it has three parts separated by semicolons in parentheses. General entry:

for(first; second; third);

Inside the parentheses, the semicolon is the delimiter, not the end of the line.

first – any instruction that the machine will execute once at the very beginning of the loop, for example, you can initialize a variable.

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Goal: write JavaScript code that calculates how much 2^10 is using a loop.

Solution:

varnum=2;
varpower=10;
varresult=1;
var subpower=1
while (subpower<=power){result*=num;subpower++};
document.write(result)

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JavaScript code can be written in any notepad and saved with a .js extension – you can also embed the code in an html page using the <script>…</script> tags in both the head and body sections. It is better to insert the body into the body of the site, this will speed up the loading of the content of the site itself.

Thus, you can create a file on your computer with the html or htm extension, in which you can prepare the following code:

<html>
<script>

your JavaScript code

</script>
</html>

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A loop is a piece of code that repeats a certain number of times. The number of repetitions or the number of iterations is described with a counter.

The loop is written with while(an expression that is converted to a boolean type -> for the next iteration, you need to get true, as soon as we get false, the loop will stop);

An example of an infinite loop: while (true);

Which translates to false in JavaScript:

• false
  undefined
  null
  0
  ” “
  NaN

Everything else is true.

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Inside the html code, you can insert and execute JavaScript using the <script>…</script> tags, which can be inserted into the head of the page.

Data output is different depending on the interpreter:

var cat = “vera”; //cat’s name
document.write(‘Hi, ‘ + cat); print the result to the user
print(‘Hi, ‘ + cat); //one output in the Visual console, but in the browser this function starts printing the page on the printer
console.log(‘Hi, ‘ + cat); //another output option, works in the Google Chrome console
Hi, Vera //result

How to use external file in code?

To connect files in JavaScript, use the src (search) function inside the tags <script src=”file name”>…</script>

A comment is a piece of code that is not interpreted. There are multi-line comments and single-line comments.

Multiline comment starts with /* and ends with */

JavaScript code
/*
a comment
for a few
lines
*/
JavaScript code

A single line comment starts with // and goes to the end of the line

JavaScript code //comment for one line

Comments in the code are needed for developers who may want to fix or complete something in the code. It is important to leave comments along the code so that users and other developers can easily understand the code.

In JavaScript, it is customary to name variables in small letters (if the name is one word) – cat; If the variable name consists of two words, then camel case notation is used, i.e. the first word is written in small letters, and the second is glued to the first and written with a capital letter: myCat; If there are several words, then the first one is written with a small letter, and each new word is glued with the previous ones and is written with a capital letter: myDearCat;

It is customary to declare variables using the var keyword, i.e. each new variable must be written on a separate line: var cat;

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Comparison operator > / <

If we write 2 < 6 , we thus ask the question, is it true or not? The answer can be in the form of boolean values – True / False.

true > false

Equality operator (soft equals) ==

We ask, 6 == 6 (six equals six), the answer will be true

We cannot compare variables of different types, that is, we cannot compare a number and a string. If we write 6 == “6” then we are asking if the number six is equal to the string six. In this case, we will also get true, because the string will be converted to a number.

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Java programming language or Java script – JavaScript – was created by a fun programmer in 10 days. Almost as God created the Earth, so Brendan Eich created a programming language in 1995 that is compatible with all browsers and is still the most popular programming language for web applications and websites.

JavaScript language features:

• interpretive
• register (case) sensitive
• embedded in html, etc.

The core of the language is ECMAScript-262, where the main constructs and syntax are described.
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