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| 1 | +# Episode 14 : First class and Anonymous functions |
| 2 | + |
| 3 | +(there is no Episode 13 idk why lol) |
| 4 | + |
| 5 | +#### Function statement : Just your normal function definition |
| 6 | + |
| 7 | +``` |
| 8 | +function a() { |
| 9 | + console.log("a called"); |
| 10 | +} |
| 11 | +a(); |
| 12 | + |
| 13 | +``` |
| 14 | + |
| 15 | +#### Function Expression : Assigning a function to a variable. Function acts like a value |
| 16 | + |
| 17 | +``` |
| 18 | +var b = function() { |
| 19 | + console.log("b called"); |
| 20 | +} |
| 21 | +b(); |
| 22 | + |
| 23 | +``` |
| 24 | + |
| 25 | +**Difference btw function statement and expression is Hoisting** |
| 26 | +- You can put "a();" before "function a()" and it will still work. But putting "b();" before "var b = function()" throws a typeError. |
| 27 | +- Why? During mem creation phase a is created in memory and function assigned to a. But b is created like a variable (b:undefined) and until code reaches the function() |
| 28 | +part, it is still undefined. So it cannot be called. |
| 29 | + |
| 30 | +#### Function Declaration : Exactly same as function statement |
| 31 | + |
| 32 | +#### Anonymous Function : A function without a name |
| 33 | +- They don't have their own identity. So an anony function without code inside it results in an error. |
| 34 | +- Anony functions are used when functions are used as values eg. the code sample for function expression above |
| 35 | + |
| 36 | +#### Named Function Expression : Same as Function Expression but function has a name instead of being anonymous |
| 37 | +``` |
| 38 | +var b = function xyz() { |
| 39 | + console.log("b called"); |
| 40 | +} |
| 41 | +b(); // prints "b called" properly |
| 42 | +xyz(); // Throws ReferenceError:xyz is not defined. |
| 43 | + |
| 44 | +``` |
| 45 | +> xyz function is not created in global scope. So it can't be called. |
| 46 | + |
| 47 | +#### Parameters vs Arguments |
| 48 | +``` |
| 49 | +var b = function(param1, param2) { // labels/identifiers that get the arg values |
| 50 | + console.log("b called"); |
| 51 | +} |
| 52 | +b(arg1, arg2); // arguments - values passed inside function call |
| 53 | + |
| 54 | +``` |
| 55 | +#### First Class Function aka First Class Citizens |
| 56 | +- You can pass functions inside a function as arguments(WOW!) |
| 57 | + |
| 58 | +``` |
| 59 | +var b = function(param1) { |
| 60 | + console.log(param1); // prints " f() {} " |
| 61 | +} |
| 62 | +b(function(){ |
| 63 | + |
| 64 | +}); |
| 65 | + |
| 66 | +this can also be done: |
| 67 | + |
| 68 | +var b = function(param1) { |
| 69 | + console.log(param1); |
| 70 | +} |
| 71 | +function xyz(){ |
| 72 | + |
| 73 | +} |
| 74 | +b(xyz); // same thing as prev code |
| 75 | + |
| 76 | +you can return a function from a function: |
| 77 | + |
| 78 | +var b = function(param1) { |
| 79 | + return function() { |
| 80 | + |
| 81 | + } |
| 82 | +} |
| 83 | +console.log(b()); //we log the entire fun within b. |
| 84 | + |
| 85 | +``` |
| 86 | +#### Arrow Functions (latest in ES6 (ECMAScript 2015) |
| 87 | + |
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