Use single quotes '' for strings.
// bad
var name = "Bob Parr";
// good
var name = 'Bob Parr';
// bad
var fullName = "Bob " + this.lastName;
// good
var fullName = 'Bob ' + this.lastName;
Strings longer than 100 characters should be written across multiple lines using string concatenation.
Note: If overused, long strings with concatenation could impact performance. jsPerf & Discussion.
// bad
var 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
var 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
var 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.';
When programmatically building up a string, use Array#join instead of string concatenation. Mostly for IE: jsPerf.
var items;
var messages;
var length;
var i;
messages = [{
state: 'success',
message: 'This one worked.'
}, {
state: 'success',
message: 'This one worked as well.'
}, {
state: 'error',
message: 'This one did not work.'
}];
length = messages.length;
// bad
function inbox(messages) {
items = '<ul>';
for (i = 0; i < length; i++) {
items += '<li>' + messages[i].message + '</li>';
}
return items + '</ul>';
}
// good
function inbox(messages) {
items = [];
for (i = 0; i < length; i++) {
// use direct assignment in this case because we're micro-optimizing.
items[i] = '<li>' + messages[i].message + '</li>';
}
return '<ul>' + items.join('') + '</ul>';
}