Javascript

Spread syntax
Use the Spread Syntax to expand an iterable (e.g. an object) into its components.
An example of merging with shallow clone would be:
var obj1 = { a: "b" };
var obj2 = { c: "b" };
var obj3 = { ...obj1, ...obj2 };
console.log(obj3);
obj3 contains a copy of obj1 and obj2 as they were when obj3 was created
obj3 is not a reference to the current state of obj1 and obj2
Executing asynchronous functions in series and parallel
Example snippet:
const executeInSeries = async promises => {
  var results = [];
  for (let promise of promises) {
    results.push(await promise());
  }
  return results;
};
​
const executeInParallel = promises => {
  return Promise.all(promises);
};
​
const generateTimeoutPromise = () => {
  return new Promise((resolve, _reject) => {
    setTimeout(() => {
      console.log("COMPLETE: timeoutPromise");
      resolve("RESOLVED: Complete");
    }, 2000);
  });
};
​
executeInSeries([
  generateTimeoutPromise,
  generateTimeoutPromise,
  generateTimeoutPromise
]).then(results => {
  console.log("COMPLETE: executeInSeries");
  console.log("RESOLVED: executeInSeries");
  console.log(results);
});
​
executeInParallel([
  generateTimeoutPromise(),
  generateTimeoutPromise(),
  generateTimeoutPromise()
]).then(results => {
  console.log("COMPLETE: executeInParallel");
  console.log("RESOLVED: executeInParallel");
  console.log(results);
});
.prettierrc Configuration
My preferred .prettierrc settings are:
{
  "printWidth": 140,
  "trailingComma": "es5",
  "jsxBracketSameLine": true,
  "arrowParens": "always",
  "tabWidth": 4,
  "noSemi": true
}
On a JS project I tend to turn on format on save (VSCode > Preferences > Settings > Workspace Settings > settings.json)
{
  "editor.formatOnSave": true
}
I use a .prettierignore for individual files I don't way to format within the project.
Finally I have the following setting to always turn off certain file types from formatting (VSCode > Preferences > Settings > User Settings > settings.json):
"[handlebars]": {
  "editor.formatOnSave": false
}
ESLint
ESLint apparently respects the following element of package.json:
"engines": {
    "node": ">=10.6.0"
}
I tend to also add the following .eslintrc to support ES6 features:
{
  "env": {
    "es6": true
  }
}
Javascript
npm
Last updated 2 years ago