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# Variables Assignment And Operators

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Introduction to variables, assignment and operators in JavaScript.

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### Variables Assignment And Operators

1. 1. variables, assignment and operators Thursday, September 10, 2009
2. 2. variables containers to store information that can be used later http://www.w3schools.com/JS/js_variables.asp Thursday, September 10, 2009
3. 3. Remember Algebra? 5=x+3 Thursday, September 10, 2009
4. 4. var var a; var age = 5; var name = 'John Nunemaker'; Thursday, September 10, 2009
5. 5. declaring variables only need var once, but multiple times won’t hurt you // good var age = 15; age // 15 age = 16; age // 16 age = 17; age // 17 // no point var age = 15; age // 15 var age = 16; age // 16 var age = 17; age // 17 Thursday, September 10, 2009
6. 6. undeclared variables automatically declare, but don’t do this x = 10; foo = 'bar'; x // 10 foo // "bar" Thursday, September 10, 2009
7. 7. variables can store anything var age = 15; var name = 'John'; var colors = ['red', 'green', 'blue']; var person = {name:'John', age:15}; var cool = true; var foo = function() { return 'bar'; } Thursday, September 10, 2009
8. 8. naming variables case sensitive var car = 'Ford'; var cAr = 'Toyota'; car // "Ford" cAr // "Toyota" Thursday, September 10, 2009
9. 9. naming variables must begin with letter or underscore var car; // good! var car9; // good! var _car; // good! var 9car; // bad! SyntaxError Thursday, September 10, 2009
10. 10. naming variables can be short or descriptive var x; // short var field; // descriptive Thursday, September 10, 2009
11. 11. naming variables separate words with underscores var section_field_name; // good idea var sectionfieldname; // bad idea Thursday, September 10, 2009
12. 12. naming variables general formatting rules for easier reading var age = 15; // good idea var age=15; // bad idea var age = 15; // bad idea Thursday, September 10, 2009
13. 13. (pause for review and applause) Thursday, September 10, 2009
14. 14. good or bad? var section; Thursday, September 10, 2009
15. 15. good or bad? var section; Thursday, September 10, 2009
18. 18. good or bad? var ﬁeldname; Thursday, September 10, 2009
19. 19. good or bad? var ﬁeldname; Should be: var ﬁeld_name; Thursday, September 10, 2009
20. 20. good or bad? var section_ﬁeld_name; Thursday, September 10, 2009
21. 21. good or bad? var section_ﬁeld_name; Thursday, September 10, 2009
22. 22. operators assignment and comparison http://www.w3schools.com/JS/js_operators.asp Thursday, September 10, 2009
23. 23. arithmetic operators operator meaning example result + addition 5+5 10 - subtraction 5-4 1 * multiplication 2*5 10 / division 1/4 0.25 % modulus 5%4 1 ++ increment x++ x+1 -- decrement x-- x-1 Thursday, September 10, 2009
24. 24. assignment operators operator example result same as = var a = 5; 5 += a += 5; 10 a = a + 5; -= a -= 5; 0 a = a - 5; *= a *= 2; 10 a = a * 2; /= a /= 2; 2.5 a = a / 2; %= a %= 4; 1 a = a % 4; Thursday, September 10, 2009
25. 25. comparison operators http://www.w3schools.com/JS/js_comparisons.asp operator meaning example result == equal to value 5 == 5 TRUE equal to value === true === 1 FALSE and type != not equal 5 != 4 TRUE > greater than 5>4 TRUE < less than 5<4 FALSE greater than >= 5 >= 5 TRUE or equal to less than <= 5 <= 5 TRUE or equal to Thursday, September 10, 2009
26. 26. logical operators operator meaning example result && and 5 == 5 && 4 != 6 TRUE || or 4 == 6 || 5 == 5 TRUE ! not !(5 == 4) TRUE Thursday, September 10, 2009
27. 27. putting it all together Thursday, September 10, 2009
28. 28. var a = 5; a += 3; a Thursday, September 10, 2009
29. 29. var a = 5; a += 3; a // 8 Thursday, September 10, 2009
30. 30. var a = 2; var b = 5; a * b; Thursday, September 10, 2009
31. 31. var a = 2; var b = 5; a * b; // 10 Thursday, September 10, 2009
32. 32. var a = 2; var b = 3; var c = a + b; var d = c * a; d Thursday, September 10, 2009
33. 33. var a = 2; var b = 3; var c = a + b; var d = c * a; d // 10 Thursday, September 10, 2009
34. 34. var blue = 'blue'; var red = 'red'; var colors = [blue, red]; colors Thursday, September 10, 2009
35. 35. var blue = 'blue'; var red = 'red'; var colors = [blue, red]; colors // ["blue","red"] Thursday, September 10, 2009
36. 36. var a = 5; a = 6; a = 7; a -= 2; a Thursday, September 10, 2009
37. 37. var a = 5; a = 6; a = 7; a -= 2; a // 5 Thursday, September 10, 2009
38. 38. var person = {name:'Peyton Manning'} person.name Thursday, September 10, 2009
39. 39. var person = {name:'Peyton Manning'} person.name // "Peyton Manning" Thursday, September 10, 2009
40. 40. var tv_shows = ['Wipeout', 'How I Met Your Mother', 'Big Bang Theory']; tv_shows[1] == 'How I Met Your Mother' Thursday, September 10, 2009
41. 41. var tv_shows = ['Wipeout', 'How I Met Your Mother', 'Big Bang Theory']; tv_shows[1] == 'How I Met Your Mother' // true Thursday, September 10, 2009
42. 42. var a = 5; var b = 4; var check = a == 5 && b == 3 check Thursday, September 10, 2009
43. 43. var a = 5; var b = 4; var check = a == 5 && b == 3 check // false Thursday, September 10, 2009
44. 44. var a = 5; var b = 4; var check = a == 3 || b > 3 check Thursday, September 10, 2009
45. 45. var a = 5; var b = 4; var check = a == 3 || b > 3 check // true Thursday, September 10, 2009
46. 46. var a = 5 - 1; a > 4 Thursday, September 10, 2009
47. 47. var a = 5 - 1; a > 4 // false Thursday, September 10, 2009
48. 48. time to program + - * / % = == === != && || ! += -= /= *= http://www.w3schools.com/JS/tryit.asp?ﬁlename=tryjs_intro Thursday, September 10, 2009