13 Noteworthy Points from Google’s JavaScript Style Guide

Don’t use var anymore

Declare all local variables with either <em class="markup--em markup--pullquote-em"><span style="color: #000000;">const</span></em> or <em class="markup--em markup--pullquote-em"><span style="color: #000000;">let</span></em>. Use const by default, unless a variable needs to be reassigned. The <em class="markup--em markup--pullquote-em"><span style="color: #000000;">var</span></em> keyword must not be used.

Arrow functions are preferred

Arrow functions provide a concise syntax and fix a number of difficulties with <em class="markup--em markup--pullquote-em"><span style="color: #000000;">this</span></em>. Prefer arrow functions over the <em class="markup--em markup--pullquote-em"><span style="color: #000000;">function</span></em> keyword, particularly for nested functions

Use template strings instead of concatenation

Use template strings (delimited with <span style="color: #000000;">`</span>) over complex string concatenation, particularly if multiple string literals are involved. Template strings may span multiple lines.

// bad
function sayHi(name) {
  return 'How are you, ' + name + '?';
}

// bad
function sayHi(name) {
  return ['How are you, ', name, '?'].join();
}

// bad
function sayHi(name) {
  return `How are you, ${ name }?`;
}

// good
function sayHi(name) {
  return `How are you, ${name}?`;
}

“for… of” is the preferred type of ‘for loop’

With ES6, the language now has three different kinds of <span style="color: #000000;">for</span> loops. All may be used, though <span style="color: #000000;">for</span>–<span style="color: #000000;">of</span> loops should be preferred when possible.

Constants should be named in ALL_UPPERCASE separated by underscores

Constant names use <span style="color: #000000;">CONSTANT_CASE</span>: all uppercase letters, with words separated by underscores.