{ "JavaScript": undefined }
By: Colten Rouska
var Javascript = ...
JavaScript ("JS" for short) is a full-fledged dynamic programming language that, when applied to an HTML document, can provide dynamic interactivity on websites.
var nodeJs = ...
Node.js is a packaged compilation of Google’s V8 JavaScript engine, the libuv platform abstraction layer, and a core library, which is itself primarily written in JavaScript.
The basic rules
- If you can take a shortcut use it
var something = {};
if(something){ ... }ES5 Vs es6
var logger = require('logger');
function addTwo(num1, num2){
logger.log('adding some numbers');
return num1 + num2;
}
function addTen(num){
return num + 10;
}
var multiByThree = function(num){
return num * 3;
}
module.exports = {
addTwo: addTwo,
addTen: addTen,
multiBythree: multiByThree
};import logger from 'logger';
let addTwo = (num1, num2) => {
logger.log('adding some numbers');
return num1 + num2;
};
function addTen (num) {
return num + 10;
};
let multiByThree = num => {
return num * 3;
}
export default {
addTwo,
addTen,
multiByThree
};Pitfalls
Variable hoisting
lexical scoping
undefined and NaN are not constants. They are global variables, and you can change their values. That should not be possible, and yet it is. Don’t do it.
function example(){
if(context){
var text = 'right';
// What is text?
} else {
// is text accessible here?
// if it is, what is it?
}
return text; // Is text out here?
}Var
function example(){
var text;
if(context){
text = 'right';
// text is 'right'
} else {
// text is defined but will return undefined
}
return text; // if context is true text = 'right' else undefined
}Var answer
function example(){
if(context){
let text = 'right';
// What is text?
} else {
// is text accessible here?
// if it is, what is it?
}
return text; // Is text out here?
}Let
Do you know your stuff?
Named Functions
Object Variables
Classes vs Closures
Objects are passed around by reference. They are never copied
Named Functions
let myFunctions = {
doThings: function(){
throw new Error('broken');
},
doStuff: function doStuff(){
throw new Error('broken');
}
};What is the difference?
function MyClass() {}
MyClass.prototype.doThings = function(){
throw new Error('Broken');
};
MyClass.prototype.doStuff = function doOtherStuff() {
throw new Error('Broken');
};Object Variables
var fruit = {
apple: {},
banana: {},
'orange': {} // does the string change anything?
};
// Does this get apple?
var apple = fruit.apple;
// Does this get banana?
var banana = fruit['banana'];What is the difference?
classes vs closures
function(logger) {
return {
logThings: function(text){
logger.log(text);
};
};
}What is the difference? Is there a difference?
class MyClass {
constructor(logger){
this.logger = logger;
}
logStuff: function(text){
this.logger.log(text);
}
}function MyClass(logger) {
this.logger = logger;
}
MyClass.prototype.logStuff = function (text) {
this.logger.log(text);
};Few classical programmers found prototypal inheritance to be acceptable, and classically inspired syntax obscures the language’s true prototypal nature. It is the worst of both worlds.
Objects are passed around by reference. They are never copied
undefined and NaN are not constants. They are global variables, and you can change their values. That should not be possible, and yet it is. Don’t do it.
When used inside of a function, the var statement defines the function’s private variables.
JavaScript Practices
By Colten Rouska (Rizowski)
JavaScript Practices
- 547
