Useful Javascript ES6 nuggets

Important points I noted while revising Javascript ES6:

:> Adding external script to webpage:

<script type="module" src="index.js"></script>

:> Exporting function to Share a Code Block:

export const add = (x, y) => {
  return x + y;
}

*Export multiple things by repeating for each export.

:> Reusing JavaScript Code Using import:

import { add, subtract } from './math_functions.js';

*Here ./ tells the import to look for the math_functions.js file in the same folder as the current file.

:> Import Everything from a File and use specific functions:

import * as myMathModule from "./math_functions.js";
myMathModule.add(2,3);
myMathModule.subtract(5,3);

:> For default export functions, while importing, no need to add braces {}, and name can be anything, not compulsorily the name of the function.

:> Promise: task completes, you either fulfill your promise or fail to do so, with two parameters - resolve and reject, to determine the outcome of the promise. Syntax:

const myPromise = new Promise((resolve, reject) => {
  if(condition here) {
    resolve("Promise was fulfilled");
  } else {
    reject("Promise was rejected");
  }
});

:> When you make a server request it takes some amount of time, and after it completes you usually want to do something with the response from the server. The then method is executed immediately after your promise is fulfilled with resolve, eg:

myPromise.then(result => {});

:> Catch can be executed if after a promise's reject method is called:

myPromise.catch(error => {});