Else 每次都有效，而如果我删除 Else 块，一切都会完美[关闭]

Question

所以这是我的代码

stem = "/*smth*/"
for (var i = stem.length - 1; i >= 0; i--) {
    if (stem[i] == 'ա' && stem[i-1] == 'ե' && stem[i+1] != undefined) {
        var alternated = stem.slice(0, i) + stem.slice(i+1)
    } else if (stem[i] == 'ե' && stem[i+1] == 'ւ' && stem[i+2] != undefined) {
        var alternated = stem.slice(0, i) + "ի" + stem.slice(i+1)
    } else if (stem[i] == 'ո' && stem[i+1] == 'յ' && stem[i+2] != undefined) {
        var alternated = stem.slice(0, i+1) + "ւ" + stem.slice(i+2)
    } else if (stem[i] == 'ո' && stem[i+1] == 'ւ' && stem[i+2] != undefined) {
        var alternated = stem.slice(0, i) + stem.slice(i+2)
    } else if (stem[i] == 'ի' && stem[i+1] != undefined) {
        var alternated = stem.slice(0, i) + stem.slice(i+1)
    } else if (stem[i] == 'է' && stem[i+1] != undefined) {
        var alternated = stem.slice(0, i) + "ի" + stem.slice(i+1)
    } else {
        alternated = stem
    }
}
alert(alternated)

必须在某些情况下改变

stem

的值，在其他情况下不改变，并将改变/未改变的值赋予

alternated

。但它不起作用，永远不要改变

stem

，否则声明每次都有效。如果我删除 else 语句，一切都很好。我试着用 switch 写它，它有同样的问题，没有用

default:

并且没有......工作得很好