regex - Javascript - Replacing a value located between a boundary -

let's have string "the quick brown fox jumps on lazy dog."

i want use "the" left boundary , "dog" right boundary , replace in between space returns:

"the dog"

i sort of know how replace specified string substitute value, not know how replace in between boundaries. need sort of regular expression? appreciated.

the regex use (the).+?(dog)

the string operation this:

var str = "the quick brown fox jumps on lazy dog.";  var result = str.replace(/(the).+?(dog)/, "$1 $2");  console.log(result);