Programmatically using Replace - correctly finds the search term but doesn't replace

[fi5u]

Hi, I'm using the JavaScript code to find and replace some strings. From the results in the console I can see that it is correctly finding two instances, however, the files remain unchanged. I set preview to false just incase it was true by default. But still the string is not being replaced. Have I got something wrong with the call?

var WPpaths = projectDir + '/app/wp-content/themes/' + siteName + '/assets/scss';
replace({
    regex: 'Domain',
    replacment: 'New domain',
    paths: [WPpaths],
    recursive: true,
    count: true,
    preview: false
});

[fi5u]

Sorry, just seen my spelling mistake!