(1)=設值
(2)= =比較
(3)= = =型態
(4)=> 箭頭函式
var x = 5
if (x==5) {
console.log("ok");
}
if (x===5) {
console.log("ok~");
}
var b = () => {
return "bunny-2";
};
var temp = b();
console.log(temp); // bunny-2
false:
// var x = 0;
// var x = false;
// var x = undefined
// var x = null
// 空白會錯誤 x is not defined
if (x) {
console.log("ok");
}
var score = Math.floor(Math.random() * 101);
console.log(score);
if (score >= 90) {
console.log('甲上');
} else {
if (score >= 80) {
console.log('甲');
} else {
if (score >= 70) {
console.log('乙上');
} else {
console.log('乙');
}
}
}
var score = Math.floor(Math.random() * 101);
console.log(score);
if (score >= 90) {
console.log('甲上');
} else if (score >= 80) {
console.log('甲');
} else if (score >= 70) {
console.log('乙上');
} else {
console.log('乙');
}
var d = new Date();
var hour = d.getHours();
console.log(hour);
// var hour = 17; 偵錯用
// console.log(hour);
if (8 <= hour && hour <= 11) {
console.log("上午課程");
} else if (hour == 12) {
console.log("中午用餐時間");
} else if (13 <= hour && hour <= 16) {
console.log("下午課程");
} else {
console.log("非課程時間");
}
CSS () =>var()、calc()、@media()、:nth-child()、hsl()
JS() => 執行:fuction、apple(){}、if(條件)、(條件)?: 、(匿名的函式)
(匿名的函式)
因為之後用不到這個倉庫,就不需要佔記憶體且不會影響他人
(function () {
//var showMsg_v3 = 刪除
console.log("狗溝好吃~~~~");
})();
Js{}:物件、要做的事
物件
var apple = {
//key1:value1 屬性
chinese: 100,
english: 90,
math: 70,
};
要做的事
var x = 5;
if (x == 5) {
console.log("ok");
}
「一定要+break!!!!!!!」---------------------------->重點
沒有加break時,會產生串聯效應,case1做完會接著做case2
switch (x) {
case 5:
console.log("ok"); // x=5 'ok'
console.log("hi");
var y = 88;
console.log(y);
console.log("bee");
break; //一定要加 才能關掉
case 15:
console.log("貓咪大戰六周年聽說很魔有空去聽看看"); // x=5 'ok'
default:
console.log("今天沒下雨了");
}
並且可合併case
switch (mm) {
case 4:
case 6:
case 9:
console.log("30天");
break;
}
function showTV() {
var elm = document.getElementById('inputChannel').value; //input輸入是字串
console.log(elm);
document.getElementById('demo').innerText = elm;
switch(elm){
case 20: //但是這要符合數值
console.log('ok'); //所以不出現。
}
}
解法:轉數值
var elm = parseInt(document.getElementById("inputChannel").value);
離開的方式:1.break 2.條件不成立
1.while + if
var x = 5;
while (x == 5) {
console.log('ok'); //一定會顯示 因為非0則ture
if (x == 5) {
x = 666;
console.log(x) //之後條件不符合var x = 5; 會跳出
}
}
var secret;
while (secret !== "1234") {
secret = prompt("1.網頁必須輸入通關密碼1234才會停止");
if (secret == "1234") {
break //會跳出
}
}
do {
console.log("ok");
} while (false);
3.while
var n = 0;
var x = 0;
while (n < 10) {
n++; // n = n+1
x += n; // x = n+x
}
document.getElementById("demo1_10").innerHTML = x;
會先執行一次,才判斷條件
do {
console.log("ok");
} while (false);
for(囉嗦) => 已知次數
while(條件) => 次數未知
(1)for
for (var i = 0; i < 10; i++) { //一行做判斷
if (i % 2 == 0) {
// 跳過這一次不做 ,2 4 6 byebye
continue;
}
if (i == 7) {
// 跳出
break;
}
console.log(i);
}
(2)while
var secret;
while (secret !== "1234") {
secret = prompt("1.網頁必須輸入通關密碼1234才會停止");
if (secret == "1234") {
break
}
}
cnt =cnt+1
cnt++
cnt += 1
innerText會是寫內文,所以要改innerHTML
會印出字串
star = star + "<br>"; //換行
document.getElementById("pSquare").innerText = star;
改
star = star + "<br>"; //換行
document.getElementById("pSquare").innerHTML = star;
(1)for():可以直接抓始末 (抓自己想要的範圍~~)
var weekList = ["sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"];
for (var i = 0; i < weekList.length; i++) {
// []從0開始
// length 有幾個
console.log(weekList[i]); //跑幾次就顯示幾次
}
(2)for(..of..):每個都要抓時使用(通通抓起來看~~)
var weekList = ["sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"];
//of 撈出來看看元素
for (var item of weekList) { //of 放集合 ex:[]
console.log(item);
}
(1) for
var tot = 0;
for (var cnt = 1; cnt <= 10; cnt++) {
//cnt++ , cnt =cnt+1 ,cnt += 1
tot = tot + cnt;
}
console.log(`計算從 1 加到 10: ${tot}`);
(2) for + if
for (var i = 0; i < 10; i++) {
//一行做判斷
if (i % 2 == 0) {
// 跳過這一次不做 ,2 4 6 byebye
continue;
}
if (i == 7) {
// 跳出
break;
}
}
(3) for..of.. (賦值給item of 放集合 ex:[])
var weekList = ["sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"];
//of 撈出來看看元素
for (var item of weekList) {
//賦值給item of 放集合 ex:[]
}
(4) for..in..(賦值給item in 放物件) 並 只會尋「有值」的資料出來
for (var item in s1) {
//賦值給item in 放物件
console.log(item); //chinese;english;math(屬性)
console.log(s1["item"]); // s1 物件裡沒有"item字串"的屬性 undefined
console.log(s1[item]); //100;90;80 抓到值
console.log(typeof item); //string
}
辛苦了(拍拍自己)