What does "|| [];" mean?

Question

What does || [] mean in the code below? Why might this be needed?

getPair: function() {
    return this.props.pair || [];
  },

Answer 1

[] is an empty array. ||, in this context, is a guard operator.

The statement says to return this.props.pair, but if this.props.pair is falsy, an empty array will be returned instead.