I recommend using double quotes to delimit strings even though single quotes are also permitted. In addition, avoid multi-line strings. Instead, split long strings into multiple ones and concatenate them. See the examples below.
// Not good. let aVeryLongString = "Oh, supercalifragilisticexpialidocious! Even though the sound of it \ Is something quite atrocious."; // Good. let aVeryLongString = "Oh, supercalifragilisticexpialidocious! " + "Even though the sound of it" + "Is something quite atrocious.";