Awesome JavaScript Smart Techniques.

1.Ternary Operator

This is a great code saver when you want to write an if..else statement in just one line.
Longhand:

const x = 100;
let answer;
if (x > 100) {
    answer = 'greater than 100';
} else {
    answer = 'less than 100';
}

Shorhand

const answer = x > 100 ? 'greater than 100' : 'less than 100';

2.Short-circuit Evaluation

When assigning a variable value to another variable, you may want to ensure that the source variable is not null, undefined or empty.
Longhand:

if (variable1 !== null || variable1 !== undefined || variable1 !== '') {
     let variable2 = variable1;
}

Shorhand

const variable2 = variable1  || 'new';

3.Loop

This little tip is really useful if you want to perform iteration.
Longhand:

for (let i = 0; i < allImgs.length; i++)

Shorhand

for (let index of allImgs)

4.Object Property

Object literals in ES6 provides an even easier way of assigning properties to objects.
Longhand:

const obj = { x:x, y:y };

Shorhand

const obj = { x, y };

5.Arrow Functions

Classical functions are easy to read and write, but they do tend to become a bit confusing once you start nesting them in other function calls.
Longhand:

function sayHello(name) {
  console.log('Hello', name);
}

setTimeout(function() {
  console.log('Loaded')
}, 2000);

list.forEach(function(item) {
  console.log(item);
});

Shorhand

sayHello = name => console.log('Hello', name);

setTimeout(() => console.log('Loaded'), 2000);

list.forEach(item => console.log(item));