js把每个词的首字母转大写

先看效果图

//把首字母变大写
    function firstToUpperCase(id) {
        var str=document.getElementById(id).value;
        //通过“空格”符来分割成数组
        var arr=str.toLowerCase().split(" ");// ["aq","","tn"]
        let neweArr=[];
        for (var i=0; i<arr.length;i++) {
            if (arr[i]!="") {// 不为空则把首字母大写，后面的截取出来不变
                //arr[i][0] 相当于二维数组了 ["aq"]=>["Aq"]
                neweArr.push(arr[i][0].toUpperCase()+arr[i].substr(1));
            }else {
                neweArr.push(arr[i]);
            }
        }
        var showArr=neweArr.join(" ");
        document.getElementById(id).value=showArr;
    }

<input onkeyup="firstToUpperCase(this.id)"  type="text" class="form-control" id="userNameEn" name="userNameEn" placeholder="如:Linda Wang"  value="${model.userNameEn}">