Javascript Tips and Tricks

Tips and Tricks

1) Getting an array from behind to front

Given the array:

1

const animals = ['Otter', 'Badger', 'Alpaca', 'Sloth'];

We can get each item in the array from behind to front by doing this:

1
2
3
4

animals.slice(-1); // ['Otter']
animals.slice(-2); // ['Badger']
animals.slice(-3); // ['Alpaca']
animals.slice(-4); // ['Sloth']

2) Short-circuit

Instead of doing:

1
2
3

if (condition) {
    callMe();
}

You can just simply:

1

condition && callMe();

3) One liner if else statement

The long way:

1
2
3
4
5
6
7
8

const age = 10;
const legalAge = 18;

if (age >= legalAge) {
    console.log('Drink beer!');
} else {
    console.log('Drink milk or something else!');
}

The one liner way:

1

console.log(age >= legalAge ? 'Drink beer!' : 'Drink milk or something else!');

4) typeof in validation

typeof can be useful in validation data validation. Let’s say you have a simple addition function that takes 2 arguments as addends then returns the sum. You want to make use that the arguments being passed are really numbers and not objects or string. You can do that by using typeof.

1
2
3
4
5
6
7

const add = (x, y) => {
    if (typeof x !== 'number' || typeof y !== 'number') return null;
    return x + y;
};

add(1, 1); // 2
add(1, {}); // null

By this solution, you can make sure that the addends are number.

5) Assigning alternative value to a falsy variables

Say you a variable color which is undefined. You can add an alternative value to it by using the || operator.

1
2
3
4
5

const color = undefined;

const alpacaColor = color || 'green';

console.log('Alpaca color is ' + alpacaColor); // Alpaca color is green

Who wants a green alpaca?

Special thanks to contributor : Jofferson Ramirez Tiquez