script async js code example
Example 1: javascript async script
<script async src="script.js"></script>
Example 2: async await javascript
function hello() {
return new Promise((resolve,reject) => {
setTimeout(() => {
resolve('I am adam.');
}, 2000);
});
}
async function async_msg() {
try {
let msg = await hello();
console.log(msg);
}
catch(e) {
console.log('Error!', e);
}
}
async_msg(); //output - I am adam.
Example 3: script async syntax
<script src="demo_async.js" async></script>
Example 4: js async await
/* Notes:
1. written like synchronous code
2. compatible with try/catch blocks
3. avoids chaining .then statements
4. async functions always return a promise
5. function pauses on each await expression
6. A non promise value is converted to
Promise.resolve(value) and then resolved
*/
// Syntax
// Function Declaration
async function myFunction(){
await ... // some code goes here
}
// Arrow Declaration
const myFunction2 = async () => {
await ... // some code goes here
}
// OBJECT METHODS
const obj = {
async getName() {
return fetch('https://www.example.com');
}
}
// IN A CLASS
class Obj {
// getters and setter CANNOT be async
async getResource {
return fetch('https://www.example.com');
}
}
Example 5: script deferred
<script src="demo_defer.js" defer></script>