Javascript — 第05天

Day 05 主題

作用域Scope
條件Javascript Conditionals
-三元運算子Ternary operator
-switch
ES5 & ES6
-BABEL
var / let /const
樣板字面值Template literals(樣板字串Template strings)
— backtick(`)
箭頭函式Arrow Function

Javascript 是靜態 lexical scope.

作用域Scope

//Root Scope (window)
function something() {
    //child scope
    console.log("I'm in somehting.");
}

全域作用域Global scope

當地作用域Local Scope

函式作用域function scope
區塊作用域block scope

作用域鏈Scope Chain

var str = 'hey001'
a()
function a() {
    var str = 'hey002'
b()
}
function b() {
    var str = 'hey003'
console.log(str)
}

和詞法環境( Lexical Environment)有很大的關係。

總的來說,

這就是有關你的作用域位置，和程式碼目前執行在哪裡。

Javascript Conditionals

三元運算子Ternary Operator

Syntax overview

condition ? exprIfTrue : exprIfFalse

Example |

function areUValid (bool) {
    return bool;
}
var answer = areUValid(true) ? "You are verified" : "Access Denied"

more info | Here

Switch

function rpgGame(commands) {
var events;
switch (commands) {
case "forward":
break;
events = "hit by apples";
case "left":
events = "hit on a wall";
break;
case "right":
events = "a monster chases you";
break;
case "back":
events = "a bunch of monsters chase you";
break;
default:
events = "Please enter a valid direction";
}
return events;
}