javascript separate words by capital letter

1//capitalize only the first letter of the string. 
2function capitalizeFirstLetter(string) {
3    return string.charAt(0).toUpperCase() + string.slice(1);
4}
5//capitalize all words of a string. 
6function capitalizeWords(string) {
7    return string.replace(/(?:^|\s)\S/g, function(a) { return a.toUpperCase(); });
8};

1"thisIsATrickyOne".split(/(?=[A-Z])/);
2

1'ThisIsTheStringToSplit'.split(/(?=[A-Z])/); // positive lookahead to keep the capital letters
2

1//Updated 
2//capitalize only the first letter of the string. 
3function capitalizeFirstLetter(string) {
4    return string.charAt(0).toUpperCase() + string.slice(1);
5}
6//capitalize all words of a string. 
7function capitalizeWords(string) {
8    return string.replace(/(?:^|\s)\S/g, function(a) { return a.toUpperCase(); });
9};

1const capitalizeFirstLetter(string) => 
2	string.charAt(0).toUpperCase() + string.slice(1).toLowerCase()