Javascript - normalize accented greek characters

Question

I am trying to apply some kind of normalization to greek text (use lower case, remove accents and replace ς with σ). For example I would like "ἀντίθεσις" (greek polytonic) and "αντίθεσις" (modern greek) become "αντιθεσισ". I ran through unicode-table.com and wrote down which character replacements I should do.

Greek and Coptic (Range: 0370— 03FF) 
ΆΑά -> α
ΈΕέ -> ε
ΉΗή -> η
ΊΪΙίΐ -> ι
ΌΟό -> ο
ΎΫΥΰϋύ -> υ
ΏΩώ -> ω

Greek Extended (Range: 1F00— 1FFF)
ἀἁἂἃἄἅἆἇὰάᾀᾁᾂᾃᾄᾅᾆᾇᾰᾱᾲᾳᾴᾶᾷἈἉἊἋἌἍἎἏᾈᾉᾊᾋᾌᾍᾎᾏᾸᾹᾺΆᾼ -> α
ἐἑἒἓἔἕὲέἘἙἚἛἜἝῈΈ -> ε
ἠἡἢἣἤἥἦἧὴήᾐᾑᾒᾓᾔᾕᾖᾗῂῃῄῆῇἨἩἪἫἬἭἮἯᾘᾙᾚᾛᾜᾝᾞᾟῊΉῌ -> η
ἰἱἲἳἴἵἶἷὶίῐῑῒΐῖῗἸἹἺἻἼἽἾἿῘῙῚΊ -> ι
ὀὁὂὃὄὅὸόὈὉὊὋὌὍῸΌ -> ο
ὐὑὒὓὔὕὖὗὺύῠῡῢΰῦῧὙὛὝὟῨῩῪΎ -> υ
ὠὡὢὣὤὥὦὧὼώᾠᾡᾢᾣᾤᾥᾦᾧῲῳῴῶῷὨὩὪὫὬὭὮὯᾨᾩᾪᾫᾬᾭᾮᾯῺΏῼ -> ω
ῤῥῬ -> ρ

I am wondering if there is a smart way to do these replacements and avoid checking strings character by character.

1st try (thanks @Tyblitz)

normal = 'Αντίθετα με αυτό που θεωρεί η πλειοψηφία, το Lorem Ipsum δεν είναι απλά ένα τυχαίο κείμενο. Οι ρίζες του βρίσκονται σε ένα κείμενο Λατινικής λογοτεχνίας του 45 π.Χ., φτάνοντας την ηλικία του πάνω από 2000 έτη.';

pol = 'Μήγαρις ἔχω ἄλλο στὸ νοῦ μου πάρεξ ἐλευθερία καὶ γλώσσα;';

console.log(normalizeGreek(normal));
console.log(normalizePolytonicGreek(pol));

function normalizeGreek(text) {
    text = text.replace(/Ά|Α|ά/g, 'α')
        .replace(/Έ|Ε|έ/g, 'ε')
        .replace(/Ή|Η|ή/g, 'η')
        .replace(/Ί|Ϊ|Ι|ί|ΐ|ϊ/g, 'ι')
        .replace(/Ό|Ο|ό/g, 'ο')
        .replace(/Ύ|Ϋ|Υ|ύ|ΰ|ϋ/g, 'υ')
        .replace(/Ώ|Ω|ώ/g, 'ω')
        .replace(/Σ|ς/g, 'σ');
    return text;
}


function normalizePolytonicGreek(text) {
    text = text.replace(/Ά|Α|ά|ἀ|ἁ|ἂ|ἃ|ἄ|ἅ|ἆ|ἇ|ὰ|ά|ᾀ|ᾁ|ᾂ|ᾃ|ᾄ|ᾅ|ᾆ|ᾇ|ᾰ|ᾱ|ᾲ|ᾳ|ᾴ|ᾶ|ᾷ|Ἀ|Ἁ|Ἂ|Ἃ|Ἄ|Ἅ|Ἆ|Ἇ|ᾈ|ᾉ|ᾊ|ᾋ|ᾌ|ᾍ|ᾎ|ᾏ|Ᾰ|Ᾱ|Ὰ|Ά|ᾼ/g, 'α')
        .replace(/Έ|Ε|έ|ἐ|ἑ|ἒ|ἓ|ἔ|ἕ|ὲ|έ|Ἐ|Ἑ|Ἒ|Ἓ|Ἔ|Ἕ|Ὲ|Έ/g, 'ε')
        .replace(/Ή|Η|ή|ἠ|ἡ|ἢ|ἣ|ἤ|ἥ|ἦ|ἧ|ὴ|ή|ᾐ|ᾑ|ᾒ|ᾓ|ᾔ|ᾕ|ᾖ|ᾗ|ῂ|ῃ|ῄ|ῆ|ῇ|Ἠ|Ἡ|Ἢ|Ἣ|Ἤ|Ἥ|Ἦ|Ἧ|ᾘ|ᾙ|ᾚ|ᾛ|ᾜ|ᾝ|ᾞ|ᾟ|Ὴ|Ή|ῌ/g, 'η')
        .replace(/Ί|Ϊ|Ι|ί|ΐ|ἰ|ἱ|ἲ|ἳ|ἴ|ἵ|ἶ|ἷ|ὶ|ί|ῐ|ῑ|ῒ|ΐ|ῖ|ῗ|Ἰ|Ἱ|Ἲ|Ἳ|Ἴ|Ἵ|Ἶ|Ἷ|Ῐ|Ῑ|Ὶ|Ί/g, 'ι')
        .replace(/Ό|Ο|ό|ὀ|ὁ|ὂ|ὃ|ὄ|ὅ|ὸ|ό|Ὀ|Ὁ|Ὂ|Ὃ|Ὄ|Ὅ|Ὸ|Ό/g, 'ο')
        .replace(/Ύ|Ϋ|Υ|ΰ|ϋ|ύ|ὐ|ὑ|ὒ|ὓ|ὔ|ὕ|ὖ|ὗ|ὺ|ύ|ῠ|ῡ|ῢ|ΰ|ῦ|ῧ|Ὑ|Ὓ|Ὕ|Ὗ|Ῠ|Ῡ|Ὺ|Ύ/g, 'υ')
        .replace(/Ώ|Ω|ώ|ὠ|ὡ|ὢ|ὣ|ὤ|ὥ|ὦ|ὧ|ὼ|ώ|ᾠ|ᾡ|ᾢ|ᾣ|ᾤ|ᾥ|ᾦ|ᾧ|ῲ|ῳ|ῴ|ῶ|ῷ|Ὠ|Ὡ|Ὢ|Ὣ|Ὤ|Ὥ|Ὦ|Ὧ|ᾨ|ᾩ|ᾪ|ᾫ|ᾬ|ᾭ|ᾮ|ᾯ|Ὼ|Ώ|ῼ/g, 'ω')
        .replace(/ῤ|ῥ|Ῥ/g, 'ρ')
        .replace(/Σ|ς/g, 'σ');
    return text;
}

2nd try:

Check my answer below which makes use of String.prototype.normalize() and prevents you from keeping lists with all the greek accented characters from the unicode table.

Answer 1

I have also found the following solution which makes use of: String.prototype.normalize()

normal = 'Αντίθετα με αυτό που θεωρεί η πλειοψηφία, το Lorem Ipsum δεν είναι απλά ένα τυχαίο κείμενο. Οι ρίζες του βρίσκονται σε ένα κείμενο Λατινικής λογοτεχνίας του 45 π.Χ., φτάνοντας την ηλικία του πάνω από 2000 έτη.';

pol = 'Μήγαρις ἔχω ἄλλο στὸ νοῦ μου πάρεξ ἐλευθερία καὶ γλώσσα;';

console.log(normalizeGreek(normal));
console.log(normalizePolytonicGreek(pol));

function normalizeGreek(text) {
    return text.normalize('NFD').replace(/[\u0300-\u036f]/g, "");
}


function normalizePolytonicGreek(text) {
    return text.normalize('NFD').replace(/[\u0300-\u036f]/g, "");
}

How it works + example:

Inside .normalize('NFD'), accented characters are decomposed to:

• the character itself
• followed by the equivalent Combining Diacritical Mark (see: range [0300-036f])

Removing these marks is easy by using: .replace(/[\u0300-\u036f]/g, "")

a = "ἄ"
console.log(a);             // prints: ἄ
console.log(Array.from(a)); // prints: [ "ἄ" ]

b = a.normalize('NFD')
console.log(b);             // prints: ἄ 
console.log(Array.from(b)); // prints: [ "α", "̓", "́" ]

c = a.normalize('NFD').replace(/[\u0300-\u036f]/g, "")
console.log(c);             // prints: α
console.log(Array.from(c)); // prints: [ "α" ]

Interesting links:

• Unicode® Standard Annex #15 - Unicode Normalization Forms
• Normalization charts
• Remove accents/diacritics in a string in JavaScript