Typescript - object is possibly null-CodePudding

I am creating simple function to count all existing vowels in given string. I wrote function to do it but I cannot compile this with Typescript version higher than 3. I am curious how this function should be written to pass Typescript versions higher than 3.

function getCount(str: string = ''): number {
      return str.match(/[aeiou]/gi).length;
    }

test:

describe("getCount", function(){
    it ("should pass a sample test", function(){
        assert.strictEqual(getCount("abracadabra"), 5)
    });
});

With Typescript version 2.4 everything passes but with higher versions I am getting this:

error TS2531: Object is possibly 'null'.

CodePudding user response：

This is because .match() will return null if there is no match found.

If it is null then length cannot be used. You could save the outcome of str.match(/[aeiou]/gi) to a variable and then check it is not null. The resulting function could look like this:

function getCount(str: string = ''): number {
  let matched = str.match(/[aeiou]/gi);
  if(matched) return matched.length;
  else return 0;
}

Look here to find more about match.