Make translation function not translate result again

Question

I have made this very simplified version of a translation tool similar to Google Translate. The idea is to build this simple tool for a minority language in sweden called "jamska". The app is built up with a function that takes the string from a textarea with the ID #svenska and replaces words in the string using RegExp.

I've made an array called arr that's used in a for loop of the function as a dictionary. Each array item looks like this: var arr = [["eldröd", "eillrau"], ["oväder", "over"] ...]. The first word in each array item is in swedish, and the second word is in jamska. If the RegExp finds a matching word in the loop it replaces that word using this code:

function translate() {

var str = $("#svenska").val();
var newStr = "";
for (var i = 0; i < arr.length; i++) {
    var replace = arr[i][0];
    var replaceWith = arr[i][1];
    var re = new RegExp('(^|[^a-z0-9åäö])' + replace + '([^a-z0-9åäö]|$)', 'ig');
    str = str.replace(re, "$1" + replaceWith + '$2');
}

$("#jamska").val(str);

}

The translate() is then called in an event handler for when the #svenska textarea gets a keyup, like this: $("#svenska").keyup(function() { translate(); });

The translated string is then assigned as the value of another textarea with the ID #jamska. So far, so good.

I have a problem though: if the translated word in jamska also is a word in swedish, the function translates that word too. This problem is occurring because I'm assigning the variable str to the translated version of the same variable, using: str = str.replace(re, "$1" + replaceWith + '$2');. The function is using the same variable over and over again to perform the translation.

Example: The swedish word "brydd" is "fel" in jamska. "Fel" is also a word in swedish, so the word that I get after the translation is "felht", since the swedish word "fel" is "felht" in jamska.

Does anyone have any idea for how to work around this problem?

Answer 1

Instead of looking for each Jamska word in the input and replacing them with the respective translation, I would recommend to find any word ([a-z0-9åäö]+) in your text and replace this word either with its translation if one is found in the dictionary or with itself otherwise:

//var arr = [["eldröd", "eillrau"], ["oväder", "over"] ...]
// I'd better use dictionary instead of array to define your dictionary 
var dict = {
    eldröd: "oväder",
    eillrau: "over"
    // ...
};
var str = "eldröd test eillrau eillrau oväder over";
var translated = str.replace(/[a-z0-9åäö]+/ig, function(m) {
    var word = m.toLowerCase();
    var trans = dict[word];
    return trans === undefined ? word : trans;
});
console.log(translated);

---

Update:

If dictionary keys may be represented by phrases (i.e. technically appear as strings with spaces), the regex should be extended to include all these phrases explicitly. So the final regex would look like

(?:phrase 1|phrase 2|etc...)(?![a-z0-9åäö])|[a-z0-9åäö]+

It will try to match one of the phrases explicitly first and only then single words. The (?![a-z0-9åäö]) lookbehind helps to filter out phrases immediately followed by letters (e.g. varken bättre eller sämreåäö).

Phrases immediately preceded by letters are implicitly filtered out by the fact that a match is either the fist one (and therefore is not preceded by any letter) or it's not the first and therefore the previous one is separated from the current by some spaces.

//var arr = [["eldröd", "eillrau"], ["oväder", "over"] ...]
// I'd better use dictionary instead of array to define your dictionary 
var dict = {
    eldröd: "oväder",
    eillrau: "over",
    bättre: "better",
    "varken bättre eller sämre": "vär å int viller",
    "test test": "double test"
    // ...
};

var str = "eldröd test eillrau eillrau oväder over test test ";
str += "varken bättre eller sämre ";
str += "don't trans: varken bättre eller sämreåäö";
str += "don't trans again: åäövarken bättre eller sämre";

var phrases = Object.keys(dict)
    .filter(function(k) { return /\s/.test(k); })
    .sort(function(a, b) { return b.length - a.length; })
    .join('|');
var re = new RegExp('(?:' + phrases + ')(?![a-z0-9åäö])|[a-z0-9åäö]+', 'ig');

var translated = str.replace(re, function(m) {
    var word = m.toLowerCase();
    var trans = dict[word];
    return trans === undefined ? word : trans;
});
console.log(translated);