```
var isOneEditDistance = function(s, t) {
if (s === t || Math.abs(s.length - t.length) > 1) return false;
let i = 0;
let j = 0;
let isEdited = false;
while (i < s.length && j < t.length) {
if (s[i] === t[j]) {
i++;
j++;
} else if (isEdited) {
return false;
} else if (s.length < t.length) { // insert into s or delete from t
j++;
isEdited = true;
} else if (s.length > t.length) { // insert into t or delete form s
i++;
isEdited = true;
} else { // edit s or t
i++;
j++;
isEdited = true;
}
}
return true;
```

Not exactly terse, but it's easy to see exactly what's going on.