Javascript — 第04天
IPFS
在JavaScript 字串是用單引號 ‘ 或雙引號 “ 包住的字。
用單引號 ‘ 或雙引號 “ 都是一樣的,沒有特別。
函式Function
function sing(song){ console.log (song) } sing('hey you');
也可用來計算
function multiply(a,b){ return a; return a * b; return b; } multiply(5, 10);
什麼是結果呢?
只有第一個值被回傳。
在 Javascript中, 一個函式 (function)也是變數(variable)。
我們可以這麼做,如:
var a = function () {}
參數(parameters)和 引數(arguments)
資料結構(Data Structure)
- 陣列arrays
- 物件objects
陣列Arrays
內容種類可有以下
- 字串strings
- 數字numbers
- 布林值booleans
- 函式functions
- 陣列中的陣列(??)array in array(??)
在程式語言中,0是第一個元素。
//strings var list= ["apple", "banana", "kiwi", "melon"]; console.log(list[0]); //numbers var numbers = [10, 20, 30, 40]; console.log(numbers[1]); //booleans var booleans = [true, false, true, true, false]; console.log(booleans[2]); //function var functionList = [function apple(){ console.log("apple"); }] functionList
在Javascript中,註解comment是 //
var list = [ ["bunny", "kitten", "puppy", "duckey"] ]; console.log(list[0]);
物件Objects
var user = { name: "John", age: 34, hobby: "soccer", isMarried: false, } user.name user.age user.hobby user.isMarried var user = { name: "John", age: 34, hobby: "soccer", isMarried: false, favoriuteGames: ["Hollow Knight", "League of Legends", "Horizon"], motto: function() { console.log("Thats's awesome!"); } } var list = [ { username: "Bob", password: "corn" }, { username: "Nuby", password: "newbie" } ];
var user = { name: "John", age: 34, hobby: "soccer", isMarried: false, favoriuteGames: ["Hollow Knight", "League of Legends", "Horizon"], motto: function() { console.log("Thats's awesome!"); } } var list = [ { username: "Bob", password: "corn" }, { username: "Nuby", password: "newbie" } ];
Null
var emptyObj = {} var nullObj = null; emptyObj nullObj nullObj.name = "Ann"; emptyObj.name = "Ann";
迴圈Loops
for / while / do while
//for loop var todos = [ "a", "b", "c", "d" ]; var todoLength = todos.length; for (var i=0; i < todoLength; i++) { todos.pop(); } //while loop var counterOne = 10; while( counterOne > 10) { console.log("while", counterOne); counterOne--; } //do-while loop var counterTwo = 10; do { console.log("do while", counterTwo); counterTwo--; } while(counterTwo > 0);
While 和 do-while 的差異
其中一個沒有值,另一個先跑一次,才注意到條件而停止。
//for loop var todos = [ "a", "b", "c", "d" ]; var todoLength = todos.length; for (var i=0; i < todoLength; i++) { console.log(todos[i]); } todos.forEach(function(todo, i) { console.log(todo, i); })
//for loop var todos = [ "a", "b", "c", "d" ]; var todoMore = [ "a", "b", "c", "d" ]; var todoLength = todos.length; function logTodos(todo, i) { console.log(todo, i); } todos.forEach(function(todo, i) { console.log(todo, i); })
建個Facebook
var database = [ { username: "A", password: "1111" }, { username: "B", password: "2222" }, { username: "C", password: "3333" } ]; var newsfeed = [ { username: "D", password: "Sunday here." }, { username: "E", password: "It's Monday!" }, ]; function isUserValid(username, password) { for(var i=0; i < database.length; i++) { if(database[i].username === username && database[i].password === password) { return true; } } return false; } function signIn(username, password) { if(isUserValid(username, password)) { console.log(newsfeed); } else { alert("Sorry, wrong username and password!"); } } var usernamePrompt = prompt("What\'s your name?"); var passwordPrompt = prompt("What\'s your password?"); signIn(usernamePrompt, passwordPrompt);
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