Check for All or None # 39

Sometimes the patterns you want to search for may have parts of them that may or may not exist. However, it may be important to check for them nonetheless.

You can specify the possible existence of an element with a question mark, ?. This checks for zero or one of the preceding elements. You can think of this symbol as saying the previous element is optional.

For example, there are slight differences between American and British English and you can use the question mark to match both spellings.

let american = "color";
let british = "colour";
let rainbowRegex= /colou?r/;
rainbowRegex.test(american);
rainbowRegex.test(british);

Both uses of the test method would return true.