10 Practical JavaScript Tricks

/* 1. Transform the arguments object into an array.*/

var argArray = Array.prototype.slice.call(arguments);


2. Sum all the values from an array.


var numbers = [3, 5, 7, 2];
var sum = numbers.reduce((x, y) => x + y);
console.log(sum); // returns 17


3. Short circuit conditionals.


if (hungry) {
    goToFridge();
}

hungry && goToFridge()


4. Use logical OR for conditions.


function doSomething(arg1){ 
    arg1 = arg1 || 32; // if it's not already set, arg1 will have 32 as a default value
}

5. Comma operator.


let x = 1;

x = (x++, x);

console.log(x);
// expected output: 2

x = (2, 3);

console.log(x);
// expected output: 3

6. Using length to resize an array.


var array = [11, 12, 13, 14, 15];  
console.log(array.length); // 5  

array.length = 3;  
console.log(array.length); // 3  
console.log(array); // [11,12,13]

array.length = 0;  
console.log(array.length); // 0  
console.log(array); // []


7. Swap values with array destructuring.


let a = 1, b = 2
[a, b] = [b, a]
console.log(a) // -> 2
console.log(b) // -> 1


8. Shuffle elements from array.


var list = [1, 2, 3, 4, 5, 6, 7, 8, 9];
console.log(list.sort(function() {
    return Math.random() - 0.5
})); 
// [4, 8, 2, 9, 1, 3, 6, 5, 7]

9. Property names can be dynamic.

const dynamic = 'color';
var item = {
    brand: 'Ford',
    [dynamic]: 'Blue'
}
console.log(item); 
// { brand: "Ford", color: "Blue" }

10. Filtering for unique values.

const my_array = [1, 2, 2, 3, 3, 4, 5, 5]
const unique_array = [...new Set(my_array)];
console.log(unique_array); // [1, 2, 3, 4, 5]