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A simple Script

1: Lecture 7 JavaScript Senior- Lecturer: Sarsenova Zh. N.

2: A simple Script First JavaScript Page First JavaScript Page document. write(""); document. write("Hello World Wide Web"); document. write("");

3: Embedding JavaScript

4: Popup Boxes Alert box Confirm box Prompts box

5: alert(), confirm(), and prompt()

6: The typeof operator typeof operator used to find the type of a JavaScript variable.

7: Example

8: Undefined data type In JavaScript, a variable without a value, has the value undefined. The typeof is also undefined.

9: Null In JavaScript null is "nothing". It is supposed to be something that doesnt exist. Unfortunately, in JavaScript, the data type of null is an object.

10: Primitive Data

11: Complex Data

12: Line Breaks To display line breaks inside a popup box, use a back –slash followed by the character n. Example: alert(Hellon How are you?);

13: JavaScript Objects Objects in real life is for instance Students Properties: name, ID, weigh, height etc. Methods: eat, speak, walk, read, do something and etc.

14: JavaScript Objects You have already learned that JavaScript variables are containers for data values.

15: Objects Objects are variables too. Objects can contain many values

16: Example

17: Object Properties The name: values pairs are called properties.

18: Object Methods Methods are actions that can be performed on objects. Methods are stored in properties as function definitions

19: Example

20: Accessing Object Properties 2 ways Or

21: Accessing Object methods ObjectName. methodName()

22: Example

23: Do Not Declare Strings, Numbers, and Booleans as Objects! When a JavaScript variable is declared with the keyword "new", the variable is created as an object:

24: Conditional Statements Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.

25: Types of conditional statements if statement - use this statement if you want to execute some code only if a specified condition is true if. . . else statement - use this statement if you want to execute some code if the condition is true and another code if the condition is false if. . . else if. . . . else statement - use this statement if you want to select one of many blocks of code to be executed switch statement - use this statement if you want to select one of many blocks of code to be executed

26: If statement Syntax and example If (expression) Statements to be executed if expression is true

27: If . . Else statement

28: If…else if… statement syntax

29: If…else if… statement example

30: Switch Statement You should use the Switch statement if you want to select one of many blocks of code to be executed.

31: Switch statements syntax

33: The break Keyword When JavaScript reaches a break keyword, it breaks out of the switch block. This will stop the execution of more code and case testing inside the block. When a match is found, and the job is done, its time for a break. There is no need for more testing

34: The default Keyword The default keyword specifies the code to run if there is no case match:

35: JavaScript Math Objects allows you to perform mathematical tasks on numbers Math. round(x) returns the value of x rounded to its nearest integer Math. round(4. 7); // returns 5 Math. round(4. 4); // returns 4: Math. pow(x, y) returns the value of x to the power of y: Math. pow(8, 2); // returns 64 Math. sqrt(x) returns the square root of x: Math. sqrt(64); // returns 8 Math. abs(x) returns the absolute (positive) value of x: Math. abs(-4. 7); // returns 4. 7 Math. ceil(x) returns the value of x rounded up to its nearest integer: Math. ceil(4. 4); // returns 5 Math. floor(x) returns the value of x rounded down to its nearest integer: Math. floor(4. 7); // returns 4 Math. min() and Math. max() can be used to find the lowest or highest value in a list of arguments: Math. min(0, 150, 30, 20, -8, -200); // returns -200 Math. max(0, 150, 30, 20, -8, -200); // returns 150 Math. random() returns a random number between 0 (inclusive), and 1 (exclusive): Math. random();

36: Math Properties (Constants) Math. E // returns Eulers number Math. PI // returns PI Math. SQRT2 // returns the square root of 2 Math. SQRT12 // returns the square root of 1/2 Math. LN2 // returns the natural logarithm of 2 Math. LN10 // returns the natural logarithm of 10 Math. LOG2E // returns base 2 logarithm of E Math. LOG10E // returns base 10 logarithm of E

37: JavaScript Random Integers Math. random() used with Math. floor() can be used to return random integers. Math. floor(Math. random() 10); //returns a number between 0 and 9

38: Home work: read Chapter 15

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