Useful JS Tricks

[BKJang]

🔨 Get Unique Values of an Array

var j = [...new Set([1, 2, 3, 3])]
>> [1, 2, 3]

🔨 Array and Boolean

filter falsy values (0, undefined, null, false, etc.) out of an array.

myArray
    .map(item => {
        // ...
    })
    // Get rid of bad values
    .filter(Boolean);

🔨 Create Empty Objects

Create empty object __proto__ and the usual hasOwnProperty and other object methods are not exist.

let dict = Object.create(null);

// dict.__proto__ === "undefined"
// No object properties exist until you add them

🔨 Merge Objects

const person = { name: 'David Walsh', gender: 'Male' };
const tools = { computer: 'Mac', editor: 'Atom' };
const attributes = { handsomeness: 'Extreme', hair: 'Brown', eyes: 'Blue' };

const summary = {...person, ...tools, ...attributes};
/*
Object {
  "computer": "Mac",
  "editor": "Atom",
  "eyes": "Blue",
  "gender": "Male",
  "hair": "Brown",
  "handsomeness": "Extreme",
  "name": "David Walsh",
}
*/

🔨 Require Function Parameters

const isRequired = () => { throw new Error('param is required'); };

const hello = (name = isRequired()) => { console.log(`hello ${name}`) };

// This will throw an error because no name is provided
hello();

// This will also throw an error
hello(undefined);

// These are good!
hello(null);
hello('David');

🔨 Destructuring Aliases

const obj = { x: 1 };

// Grabs obj.x as { x }
const { x } = obj;

// Grabs obj.x as { otherName }
const { x: otherName } = obj;

🔨 Get Query String Parameters

// Assuming "?post=1234&action=edit"

var urlParams = new URLSearchParams(window.location.search);

console.log(urlParams.has('post')); // true
console.log(urlParams.get('action')); // "edit"
console.log(urlParams.getAll('action')); // ["edit"]
console.log(urlParams.toString()); // "?post=1234&action=edit"
console.log(urlParams.append('active', '1')); // "?post=1234&action=edit&active=1"

🙏 Reference

• 7 Useful JavaScript Tricks