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<!doctype html>
<html lang="en">
<meta charset="utf-8" />
<title>websoft</title>
<!-- Mithril HTML Slideshow styles -->
<link href="css/mithril-slideshow.css" rel="stylesheet" />
<!-- Code formatting using highlight.js -->
<link rel="stylesheet" href="css/default.css">
<link rel="stylesheet" href="css/tomorrow.css">
<script src="js/highlight.pack.js"></script>
<!-- Text formatting using Markdown through showdown.js -->
<script src="js/showdown.min.js"></script>
<script data-role="slide" data-markdown type="text/html">
# Software Development for the Web
## JavaScript Core, continued
### Mikael Roos
</script>
<script data-role="slide" data-markdown type="text/html">
# Agenda
* Mer om JavaScript core
* Scope
* Hoisting
* Closure
* Module pattern
* ES6 konstruktioner
</script>
<script data-role="slide" data-markdown type="text/html">
#strict mode
* `"use strict";`
* Filnivå men föredragsvis på funktionsnivå.
* Kastar error istället för misslyckas i tysthet
* Förenkla för intern optimering
* Bort med syntax som kan komma att försvinna
</script>
<script data-role="slide" data-markdown type="text/html">
#Scope
</script>
<script data-role="slide" data-markdown type="text/html">
#Hoisting
<pre data-code="c9"></pre>
</script>
<script id="c9" data-role="code" data-language="javascript" type="text/html">
// Not like this
function doit() {
var a = 1;
for(var i = 0; i < 42; i++) {
var b = "hej";
}
}
// Do like this (hoisting and function scope)
function doit() {
var a = 1;
var b;
var i;
for(i = 0; i < 42; i++) {
b = "hej";
}
}
</script>
<script data-role="slide" data-markdown type="text/html">
#Hoisting...
<pre data-code="c91"></pre>
</script>
<script id="c91" data-role="code" data-language="javascript" type="text/html">
// Hoists declarations
// But not assignments
function func() {
if (true) {
var tmp = 123;
}
console.log(tmp); // 123
}
// Hoisting declarations
function func() {
var tmp; // declaration is moved up to the top
if (true) {
tmp = 123; // assignment remains
}
console.log(tmp); // 123 variable function scoped
}
</script>
<script data-role="slide" data-markdown type="text/html">
#Scope function
<pre data-code="c10"></pre>
</script>
<script id="c10" data-role="code" data-language="javascript" type="text/html">
// Inner functions can access
// outer function variables
function doit() {
var a = 1;
function again() {
var b = 2;
console.log(a + b);
}
again(); // 3
}
</script>
<script data-role="slide" data-markdown type="text/html">
#Scope closure
<pre data-code="c12"></pre>
</script>
<script id="c12" data-role="code" data-language="javascript" type="text/html">
// Inner functions is always executing
// within its outer function,
// creating a closure
function doit() {
var a = 1;
function again() {
var b = 2;
a = a + b;
return a;
}
return again;
}
myAgain = doit();
myAgain(); // a === 3
myAgain(); // a === 5
</script>
<script data-role="slide" data-markdown type="text/html">
#Function as variable (siaf)
<pre data-code="c131"></pre>
</script>
<script id="c131" data-role="code" data-language="javascript" type="text/html">
// Function definition through
// function expression
myFunc = function() { console.log("hej"); }
myFunc; // A Function object
myFunc(); // Calls the function which returns "hej"
</script>
<script data-role="slide" data-markdown type="text/html">
#Siaf, iife/iffy
<pre data-code="c132"></pre>
</script>
<script id="c132" data-role="code" data-language="javascript" type="text/html">
// Function expression
myFunc = function() { console.log("hej"); }
// Immediate invoking function expression
// Self invoking anonymous function
// leaving just the return value
myString = (function() { return "hej"; })()
console.log(myString); // just the string "hej"
// or just...
(function() { return "hej"; })();
</script>
<script data-role="slide" data-markdown type="text/html">
#Siaf, iife/iffy...
<pre data-code="c13"></pre>
</script>
<script id="c13" data-role="code" data-language="javascript" type="text/html">
// or just...
(function() { return "hej"; })();
// The construct, bit by bit
function() { return "hej"; } // Function expression
(function() { return "hej"; }) // Wrap it within ()
(function() { return "hej"; })() // Add () to call it
// Sometimes called with arguments, for scope
(function(win, doc) { /* body */ })(window, document)
</script>
<script data-role="slide" data-markdown type="text/html">
#Siaf/iife till closure
<pre data-code="c14"></pre>
</script>
<script id="c14" data-role="code" data-language="javascript" type="text/html">
// Do not pollute the global scope
// Create a closure to run the code in
(function() {
var a;
// Do all stuff
})();
</script>
<script data-role="slide" data-markdown type="text/html">
#Siaf/iife till closure och modul pattern
<pre data-code="c15"></pre>
</script>
<script id="c15" data-role="code" data-language="javascript" type="text/html">
window.mos = (function() {
var a = 4;
var b = 42;
var c = function() { return "hej"; };
return {
some: a,
thing: 2,
other: function() { return b; },
ing: function() { return c(); },
}
})();
window.mos.thing; // 2
window.mos.ing(); // "hej"
</script>
<script data-role="slide" data-markdown type="text/html">
#Variationer på modul pattern
* Returnera objekt med publikt api
* Resten privat i closuret
* Alla delar som returneras lever i sitt closure när de exekveras
</script>
<script data-role="slide" data-markdown type="text/html">
#ES6 konstruktioner
* Template literal
* `var` kontra `let`
* `const`
* Spread operator `...`
</script>
<script data-role="slide" data-markdown type="text/html">
#Template literal
```
const firstName = 'Jane';
console.log(`Hello ${firstName}!
How are you
today?`);
// Output:
// Hello Jane!
// How are you
// today?
```
</script>
<script data-role="slide" data-markdown type="text/html">
#var och let
* `var` ES5 och function scope (hoisting)
* `let` ES6 och block scope
</script>
<script data-role="slide" data-markdown type="text/html">
#let/const scope
```
// Blockscope
function doit(x) {
if (x) {
let tmp = x;
}
console.log(tmp); // ReferenceError: tmp is not defined
}
// Shadow variables when blockscope
function func() {
const foo = 5;
if (···) {
const foo = 10; // shadows outer `foo`
console.log(foo); // 10
}
console.log(foo); // 5
}
```
</script>
<script data-role="slide" data-markdown type="text/html">
#let/const visibility
```
// Visible for inner functions
// (blockscope)
function doit() {
let a = 1;
function b() {
let b = a + 1;
return b;
}
return b;
}
c = doit();
c(); // 2
// Shadow variables when blockscope
function func() {
const foo = 5;
if (···) {
const foo = 10; // shadows outer `foo`
console.log(foo); // 10
}
console.log(foo); // 5
}
```
</script>
<script data-role="slide" data-markdown type="text/html">
#Constants
* Immutable
* Block scope
```
// Immutable
const foo = 'abc';
foo = 'def'; // TypeError
// Scoped to the block
function func() {
if (true) {
const tmp = 123;
}
console.log(tmp); // ReferenceError: tmp is not defined
}
```
</script>
<script data-role="slide" data-markdown type="text/html">
#Spread operator `...`
* Turn array into its pieces
```
> Math.max(-1, ...[-1, 5, 11], 3)
11
> [1, ...[2,3], 4]
[1, 2, 3, 4]
```
</script>
<script data-role="slide" data-markdown type="text/html">
#Läs på
* [ES5: Speaking JavaScript](http://speakingjs.com/)
* [ES6: Exploring ES6](http://exploringjs.com/)
</script>
<script data-role="slide" data-markdown type="text/html">
# Last words
* Questions on that?
</script>
<script data-role="slide" data-markdown type="text/html">
</script>
<!-- include essential js-script -->
<script src="js/mithril.min.js"></script>
<script src="js/mithril-slideshow.js"></script>