useful-tricks-for-javascript

original article

Get Unique Values of an Array

Getting an array of unique values is probably easier than you think:

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

Array and Boolean

Ever need to filter falsy values (0, undefined, null, false, etc.) out of an array? You may not have known this trick:

1
2
3
4
5
6
7
myArray
    .map(item => {
        // ...
    })
    // Get rid of bad values
    .filter(Boolean);
Just pass Boolean and all those falsy value go away!

Create Empty Objects

Sure you can create an object that seems empty with {}, but that object still has a proto and the usual hasOwnProperty and other object methods. There is a way, however, to create a pure “dictionary” object:

1
2
3
4
let dict = Object.create(null);

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

There are absolutely no keys or methods on that object that you don’t put there!

Get Query String Parameters

For years we wrote gross regular expressions to get query string values but those days are gone – enter the amazing URLSearchParams API:

1
2
3
4
5
6
7
8
9
// 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"

Much easier than we used to fight with!