js capitalize word

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

1const lower = 'this is an entirely lowercase string';
2const upper = lower.charAt(0).toUpperCase() + lower.substring(1);

1With performance metrics...
2
3// 10,889,187 operations/sec
4function capitalizeFirstLetter(string) {
5    return string[0].toUpperCase() + string.slice(1);
6}
7
8// 10,875,535 operations/sec
9function capitalizeFirstLetter(string) {
10    return string.charAt(0).toUpperCase() + string.slice(1);
11}
12
13// 4,632,536 operations/sec
14function capitalizeFirstLetter(string) {
15    return string.replace(/^./, string[0].toUpperCase());
16}
17
18// 1,977,828 operations/sec
19String.prototype.capitalizeFirstLetter = function() {
20    return this.charAt(0).toUpperCase() + this.slice(1);
21}
22

1function capitalizeName(name) {
2  return name.replace(/\b(\w)/g, s => s.toUpperCase());
3}
4
5

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