Javascript good parts - for novice programmers
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The document discusses various JavaScript concepts, including variable scope, data types, type coercion, and the quirks of the language such as semicolon insertion and floating point inaccuracies. It also highlights useful features of JavaScript like object literals, closures, and function objects, while providing practical examples to illustrate these topics. Overall, it serves as an exploration into both the pitfalls and strengths of JavaScript programming.
![NOT WHAT YOU EXPECT
TYPEOF()
typeof('abc’) -> string -> Nice
typeof(1) -> number -> Good
typeof({}) -> object -> Great
typeof([1,2,3]) -> object -> Ooops
typeof(null) -> object -> WTH](https://image.slidesharecdn.com/javascript-goodparts-150831100516-lva1-app6891/85/Javascript-good-parts-for-novice-programmers-9-320.jpg)
![CLOSURES, IN ACTION
var wishPeople = function(){
var names = ['manohar', 'supriya', 'hari', 'DP'];
var wish = function(){
for(i=0, n=names.length; i < n;i++) {
console.log("Hello!" + names[i] + ". Welcome to Women Who Code meetup
}
};
return wish;
}();
wishPeople();](https://image.slidesharecdn.com/javascript-goodparts-150831100516-lva1-app6891/85/Javascript-good-parts-for-novice-programmers-22-320.jpg)
Javascript good parts - for novice programmers
- 1. JAVASCRIPT - GOOD PARTS Manohar Shetty || Supriya Anand
- 2. SESSION-1 Efforts put in to make a robot called Javascript
- 3. SESSION-2 Play with javascipt - alerts, console.logs and what not.
- 4. SESSION-2 Frustated! Why somethings work and somethings don't?
- 5. I am bad... very very bad.
- 6. GLOBAL VARIABLES No linker. Global namespace. Variable collisions! //Your code function foo() { if (false) { var x = 1; } return; var y = 1; } //How Javascript interprets it function foo() { var x, y; if (false) { x = 1; } return; y = 1; }
- 7. '+' Adds and concatenates. Un-predictable and error prone 0 + "1" // returns "01" "3" + 1 // returns "31" "3" - "2" // returns 1
- 8. SEMICOLON INSERTION Semi-colons are INSERTED by the parser Optional semi-colons are not a “language feature” You are not warned!! .... 'Uh oh..' “JavaScript: where forgetting the occasional semicolon isn't necessarily the end of the world.”
- 9. NOT WHAT YOU EXPECT TYPEOF() typeof('abc’) -> string -> Nice typeof(1) -> number -> Good typeof({}) -> object -> Great typeof([1,2,3]) -> object -> Ooops typeof(null) -> object -> WTH
- 11. AGAIN.. == AND != ‘ ’ == 0 -> false 0 == ‘ ‘ -> true false == ‘false’ -> false false == ‘0’ -> true false == undefined -> false undefined == null -> true
- 13. FLOATING POINTS 0.1 + 0.2 = 0.3 //Nope, back to grade 1 you go! > 0.1 + 0.2 == 0.3 false > 0.1 + 0.2 = 0.30000000000000004 WHAT?!
- 14. STYLE IS NOT SUBJECTIVE return { status: ‘OK’ } return { status: ‘OK’ } return; { status: ‘OK’; }
- 15. OKAY, ENOUGH OF THE BAD! Show me the good!!
- 16. FINALLY, LETS TALK ABOUT THE GOOD.
- 17. OBJECT LITERALS var obj = { name: 'manohar', age: 23 } Pass as options to functions JSON for communication, remember API's anyone?
- 18. DYNAMIC OBJECTS Members can be added to any object, any time Helpful to attach attributes var obj = { count: 2, getCount: function(){ return this.count; } } obj.incrementCount = function(){ this.count++; } obj.incrementCount(); alert(obj.getCount()); // 3
- 19. LOOSELY TYPED /* JavaScript Example (loose typing) */ var a = 13; // Number declaration var b = "thirteen"; // String declaration b=a // b = 13 /* Java Example (strong typing) */ int a = 13; // int declaration String b = "thirteen"; // String declaration
- 20. FUNCTIONS ARE OBJECTS can be passed, returned var fibonacci = function(number) { number < 2 ? number : fibonacci(number -1 ) + fibonacci(number - 2) }
- 21. LAMBDA / CLOSURES a closure is a reference to the local vars for a function - local vars kept alive after the function has returned a closure is a stack-frame which is not deallocated when the function returns. (as if a 'stack-frame' were malloc'ed instead of being on the stack!) function, inner function, outer function, function inside function, this function, that function CONFUSED?
- 22. CLOSURES, IN ACTION var wishPeople = function(){ var names = ['manohar', 'supriya', 'hari', 'DP']; var wish = function(){ for(i=0, n=names.length; i < n;i++) { console.log("Hello!" + names[i] + ". Welcome to Women Who Code meetup } }; return wish; }(); wishPeople();
- 25. www.mavenhive.in