js 字符串首字母大寫

function capitalize(string){

    var words = string.split(' ');

    var i;

    for(i = 0; i < words.length; i ++){

        words[i] = words[i].charAt(0).toUpperCase()+words[i].slice(1);

    }

    console.log(words);

    return words.join(' ');

}

var str = "I am is a student";
        
console.log(capitalize(str));