JavaScript

Сентябрь 7, 2022

Содержание

2. Which one is legal? My_variable $my_variable 1my_example _my_variable @my_variable My_variable_example ++my_variable %my_variable #my_variable ~my_variable myVariableExample
3. For Loop A loop is a block of code that allows you to repeat a section
4. Why loops are useful? Loops are useful because they allow you to repeat lines of code
5. For loop for (initial_expression; test_exp; change_exp) { statements; } One of the most used and familiar
6. For loop for ( varname=1;varname initialization Tells the loops when to stop running Determines the rate
7. For loop Example var counter; for (counter = 1; counter { document.write(counter*counter + “ “); }
8. A while loop just looks at a short comparison and repeats until the comparison is no
9. While loop example While loop example var counter = 100; var numberlist = “”; while (counter
10. Do…while loop The do/while loop always executes statements in the loop in the first iteration of
11. Do…while example
12. Array An Array contains a set of data represented by a single variable name. Arrays in
13. Array Example Car = new Array(3); Car[0] = “Ford”; Car[1] = “Toyota”; Car[2] = “Honda”; document.write(Car[0]
14. Array You can also declare arrays with variable length. arrayName = new Array(); Length = 0,
15. Events The most exciting JavaScript-powered pages are dynamic. Which means they perform various actions as your
16. Syntax
17. Common HTML Events The other events we can find here: https://www.w3schools.com/jsref/dom_obj_event.asp
18. Example
19. Common HTML object events
20. Onclick event
21. Exercise When the button is clicked, trigger myFunction() with an event.
22. Mouse Events
23. Keyboard Events
24. onFocus event
25. onblur event Execute a JavaScript when a user leaves an input field:
26. onchange event
27. Frame/Object Events
28. Form Events
30. Скачать презентацию

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Which one is legal?
My_variable
$my_variable
1my_example
_my_variable
@my_variable
My_variable_example
++my_variable
%my_variable
#my_variable
~my_variable
myVariableExample

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For Loop
A loop is a block of code that allows you

to repeat a section of code a certain number of times, perhaps changing certain variable values each time the code is executed.

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Why loops are useful?
Loops are useful because they allow you to

repeat lines of code without retyping them or using cut and paste in your text editor.
They save time and trouble of repeatedly typing the same lines of code, but also avoids typing errors in repeated lines.
You are also able to change one or more variable values each time the browser passes through the loop.

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$For loop for (initial_expression; test_exp; change_exp) { statements; } One of$

For loop
for (initial_expression; test_exp; change_exp)
{ statements; }
One of the most used

and familiar loops is the for loop.
It iterates through a sequence of statements for a number of times controlled by a condition.
The change_exp determines how much has been added or subtracted from the counter variable.

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For loop
for ( varname=1;varname<11;varname+=1 )
initialization
Tells the loops when to stop running
Determines

the rate at which the variable is changed and whether it gets larger or smaller

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For loop Example

Display the square of numbers
Output: 1 4 9 16 25 36 49 64 81 100

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A while loop just looks at a short comparison and repeats

until the comparison is no longer true.
The while loop begins with a termination condition and keeps looping until the termination condition is met.
The counter variable is managed by the context of the statements inside the curly braces.
while(varname<11)
{
}

While loop

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While loop example

While loop example
…

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Do…while loop
The do/while loop always executes statements in the loop in

the first iteration of the loop.
The termination condition is placed at the bottom of the loop.
Syntax:
do {
statements;
counter increment/decrement;
} while (termination condition)

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Do…while example

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Array
An Array contains a set of data represented by a single

variable name.
Arrays in JavaScript are represented by the Array Object, we need to “new Array()” to construct this object.
The first element of the array is “Array[0]” until the last one Array[i-1].
E.g. myArray = new Array(5)
We have myArray[0,1,2,3,4].

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Array Example

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Array
You can also declare arrays with variable length.
arrayName = new Array();
Length

= 0, allows automatic extension of the length.
Car[9] = “Ford”; Car[99] = “Honda”;

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Events
The most exciting JavaScript-powered pages are dynamic. Which means they perform

various actions as your visitor interacts with them(moving his mouse, typing in the text, clicking things, and so on).
Events are notifications that an HTML element sends out when specific things happen
An HTML event can be something the browser does, or something a user does.
Examples
An HTML web page has finished loading
An HTML input field was changed
An HTML button was clicked

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