Strings

Quotes

• Use single quotes '' for strings. eslint: quotes jscs: validateQuoteMarks

// bad
const name = "Capt. Janeway";

// good
const name = 'Capt. Janeway';

Long strings

• Strings that cause the line to go over 100 characters should be written across multiple lines using string concatenation.
• Note: If overused, long strings with concatenation could impact performance. jsPerf & Discussion.

// bad
const errorMessage = 'This is a super long error that was thrown because of Batman. When you stop to think about how Batman had anything to do with this, you would get nowhere fast.';

// bad
const errorMessage = 'This is a super long error that was thrown because \
of Batman. When you stop to think about how Batman had anything to do \
with this, you would get nowhere \
fast.';

// good
const errorMessage = 'This is a super long error that was thrown because ' +
'of Batman. When you stop to think about how Batman had anything to do ' +
'with this, you would get nowhere fast.';

Template literals

• When programmatically building up strings, use template strings instead of concatenation. eslint: prefer-template template-curly-spacing jscs: requireTemplateStrings

Why? Template strings give you a readable, concise syntax with proper newlines and string interpolation features.

// 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}?`;
}

Eval()

• Never use eval() on a string, it opens too many vulnerabilities.