文字列方法---split()、join()[文字列分割、配列を文字列に変換]

/*language  
    "  ": 1,
    "  ": 2,
    "   ": 3
*/
function changeLanguage (type,languageArr) {
    if (type === 1) {
        languageArr.push('  ');
    } else if (type === 2) {
        languageArr.push('  ');
    } else if (type === 3) {
        languageArr.push('   ');
    }
}
let typeNum,
    languageArr = [],
    dubLanguageStr = "1,3",
    //split()    Array,            
    languageNum = dubLanguageStr.split(",");
for (let ele of languageNum) {
    typeNum = Number(ele);
    changeLanguage(typeNum,languageArr);
}
languageArr.join(',');
//    ：  ,