What’s the best way to do string building/concatenation in JavaScript?

With ES6, you can use

• Template strings:

  var username="craig";
  console.log(`hello ${username}`);
  

ES5 and below:

• use the + operator

  var username="craig";
  var joined = 'hello ' + username;
  

• String’s concat(..)

  var username="craig";
  var joined = 'hello '.concat(username);
  

Alternatively, use Array methods:

• join(..):

  var username="craig";
  var joined = ['hello', username].join(' ');
  

• Or even fancier, reduce(..) combined with any of the above:

  var a = ['hello', 'world', 'and', 'the', 'milky', 'way'];
  var b = a.reduce(function(pre, next) {
    return pre + ' ' + next;
  });
  console.log(b); // hello world and the milky way