/*
 * As terse as possible, assuming you're using ES version 6+
 */
var upLetter1=s=>s.replace(/./,m=>m.toUpperCase());

console.log(upLetter1("the quick brown fox jumped over the lazy dog."));
//\\ The quick brown fox jumped over the lazy dog. //\\

这就是同样的行动:

var newStr = string.slice(0,1).toUpperCase() + string.slice(1);

使用步枪功能:

const capitalize = string => string[0].toUpperCase() + string.slice(1)

这是一个简单的

const upper = lower.replace(/^\w/, c => c.toUpperCase());

带有箭功能

let fLCapital = s => s.replace(/./, c => c.toUpperCase())
fLCapital('this is a test') // "This is a test"

用火箭功能,另一种解决方案

let fLCapital = s => s = s.charAt(0).toUpperCase() + s.slice(1);
fLCapital('this is a test') // "This is a test"

与 Array 和 地图()

let namesCapital = names => names.map(name => name.replace(/./, c => c.toUpperCase()))
namesCapital(['james', 'robert', 'mary']) // ["James", "Robert", "Mary"]

s[0].toUpperCase``+s.substr`1`

let s = 'hello there' console.log( s[0].toUpperCase''+s.substr`1` )