Check if string is starting with prefix

I would like to check with javascript if array items starts with the word "prefix".

So far I've done something like this:

let array = ["prefix-word1", "prefix-word2"];

array.forEach(function(element) {
      if (element.lastIndexOf('prefix', 0) == 0) {
        console.log('prefix');
      }
    }

For some reason I keep get an error that prefix is not defined. Please help.