A must-have for programmers, the ten most commonly used code shorthand techniques in JavaScript

To determine whether a programmer is a good programmer, look at the code he writes and you can know a thing or two, because the most important thing for a programmer is to write code.

Good programmers write code that is neat and regulated, and visually naturally has a sense of beauty. Good programmers adopt consistent shorthand rules, while poor programmers sometimes don't shorthand, sometimes shorthand.

Today w3cschool editor-in-chief I put together a list of 10 programmers commonly used code shorthand technology, so that your code book shorthand neat specification has a sense of beauty, let's learn about these codes!

1, object properties shorthand

If the property name is the same as the key name, you can use ES6:

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

Shorthand:

const obj = { x, y };

2, declare the variable shorthand method

let x; l et y; let z = 3;

Shorthand:

let x, y, z=3;

3, troy operator

When you want to write if... When you use a mitso operator instead of an else statement.

const x = 20; l et answer; if (x > 10) {

Shorthand:

const answer = x > 10 ? 'is greater' : 'is lesser';

Of course, if statements can also be nested:

const big = x > 10 ? " greater 10" : x

4, short-circuit evaluation of shorthand

When assigning another value to a variable, if we want to determine that the source start value is not null, undefined, or empty, we can use the short-circuit evaluation method:

const variable2 = variable1 || 'new';

You can write an if statement that is composed with multiple criteria.

5, if the existence of conditional shorthand method

if (likeJavaScript === true)

Shorthand:

if (likeJavaScript)

The statements are equal only if the like JavaScript is true

If the judgment value is not true, you can do this:

let a; if ( a !== true ) {// do something...}

Shorthand:

let a; if ( !a ) {// do something...}

6, implicitly return value shorthand

Return statements are often used to return the final result of a function, and an arrow function with a separate statement implicitly returns its value (the function must be omitted).

In order to omit the return keyword) to return a multi-line statement, such as an object literal expression, you need to surround the function body with ().

Shorthand:

7, JavaScript loop shorthand method

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

Shorthand:

for (let index in allImgs)

You can also use Array.forEach:

8, short-circuit evaluation

A variable is assigned a value by determining whether its value is null or underfined, you can:

let dbHost; if (process.env.DB_HOST) {

Shorthand:

const dbHost = process.env.DB_HOST || 'localhost';

9, decimal index

When you need to write a number band with a lot of zeros (e.g. 10000000), you can replace that number with an index (1e7):

for (let i = 0; i < 10000; i++) {}

Shorthand:

10, the arrow function shorthand

Traditional function writing methods are easy to understand and write, but if nested in another function, these advantages disappear.

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

Shorthand:

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