packages/devtools-reps/src/reps/rep-utils.js
function interleave(items, char) {
  return items.reduce((res, item, index) => {
    if (index !== items.length - 1) {
      return res.concat(item, char);
    }
    return res.concat(item);
  }, []);
}
function interleave(items, char) {
  return items.reduce((res, item, index) => {
    if (index !== items.length - 1) {
      return res.concat(item, char);
    }
    return res.concat(item);
  }, []);
}
function interleave ( items , char ) { return items . reduce ( ( res , item , index ) => { if ( index !== items . length - 1 ) { return res . concat ( item , char ) ; } return res . concat ( item ) ; } , [ ] ) ; }
Returns new array in which `char` are interleaved between the original items.

@param {Array} items
@param {String} char
@returns Array
Returns new array in which char are interleaved between the original items .