js語法

宣告

var 宣告一個可隨意更改其內容的變數 let 宣告一個可隨意更改其內容的區塊區域變數 const 宣告一個只可讀取的不可變常數 window.thinggggggggg 全域變數 thing=['thing1','thing2'] 陣列 wtf = { wtf1: 'lol',wtf1: 'lol' }; 物件字面值 Object literals

範例:

var a=1;
console.log(a);

let x=1;
console.log(x);

var window.z=1;
console.log(window.z);

var lol = ['lol1', , 'lol2'];
console.log(lol[0]);

var wtf = { wtf1: 'lol', wtf2: function('lol'), wtf3: lol };
console.log(lol.wtf1);

if else

if (x===y){
    yes();
}
else{
    no();
}


if (x===y) {
   yes();
}
else if (x===z) {
    yessss();
}
else if (x===0) {
   yesssssssss();
}
else {
  no();
}

switch

switch (input) {
  case "1":
    console.log("1");
    break;
  case "2":
    console.log("2");
    break;
  case "3":
    console.log("3");
    break;
  default:
   console.log("0");
}

try

try { //正常
  if(0=0);
}
catch (e) { //崩潰
  logMyErrors(e);
}
finally {
  console.log("yeeeeee"); //一定會執行
}

for

  for (var i = 0; i < 10; i++) {
      console.log(i);
  }

for in

var object = [1, 2, 3];
for (input in object) {
  console.log(input) //0 1 2 (位置)
}

for of

var object = [1, 2, 3];
for (input of object) {
  console.log(input) //1 2 3 (內容)
}

do while

var i=0;
do {  //先執行
i += 1;
console.log(i);
} while (i < 2); //後檢查

while

while (true) {   //無限迴圈
  console.log("AAA");
}

while (var n < 3) {  //直到 false
  n++;
}

迴圈例外處理 brake 終止迴圈 confinue 跳回迴圈判斷

function

function lol(fuckthing){
  return fuckthing;
}