javascript toLowerCase() function returns different string

Question

console.log("HİNDİ".toLocaleLowerCase() == "hindi");
console.log("HİNDİ" == "hindi");

console.log("HİNDİ".toLowerCase());


console.log("HİNDİ".toLocaleLowerCase())
console.log("HİNDİ".toLowerCase())

I am building a search functionality but i come across a thing:

"HİNDİ".toLocaleLowerCase() // "hindi"

"hindi" == "HİNDİ".toLocaleLowerCase() //false

What the heck is going on here?

Solution: @pmrotule's answer seems to work:

function to_lower(s)
{
    var n = "";
    for (var i = 0; i < s.length; i++) // do it for one character at a time
    {
        var c = s[i].toLowerCase();

        // call replace() only if the character has a length > 1
        // after toLowerCase()
        n += c.length > 1 ? c[0].replace(/[^ -~]/g,'') : c;
    }
    return n;
}

Thanks,

Different encoding on the strings? Javascript uses UTF-16 internally. You could run "HİNDİ".toLocaleLowerCase() in your console. Also, you can try to type the character code directly. Example: "\u90AB" — Ismael Miguel
– Ismael Miguel, Commented Jun 13, 2016 at 13:36
Both UTF8, You may try it on the console too here on stackowerflow. Same result. — serkan
– serkan, Commented Jun 13, 2016 at 13:38
The current code in the updated question gives me true, false, hindi, hindi, hindi. No problem for me. Possibly locale dependent. — trincot
– trincot, Commented Jun 13, 2016 at 13:50
Seems to be browser dependent as well. For me the problem occurs in IE, not in FF. — trincot
– trincot, Commented Jun 13, 2016 at 14:07

pmrotule · Accepted Answer · 2016-06-14 08:19:41Z

3

It is a problem of string format. toLocaleLowerCase is meant for human-readable display only. However, there is still a trick you can do:

if ("hindi" == "HİNDİ".toLowerCase().replace(/[^ -~]/g,''))
{
    alert("It works!");
}

EDIT

If you want to make it works with all special characters:

function to_lower(s)
{
    var n = "";
    for (var i = 0; i < s.length; i++) // do it for one character at a time
    {
        var c = s[i].toLowerCase();
        
        // call replace() only if the character has a length > 1
        // after toLowerCase()
        n += c.length > 1 ? c.replace(/[^ -~]/g,'') : c;
    }
    return n;
}

console.log("gök" == to_lower("GÖK"));
console.log("hindi" == to_lower("HİNDİ"));

function to_low(s) // shorter version
{
    var n = "";
    for (var i = 0; i < s.length; i++)
    { n += s[i].toLowerCase()[0]; }

    return n;
}

console.log("hindi" == to_low("HİNDİ"));

edited Jun 14, 2016 at 8:19

answered Jun 13, 2016 at 13:55

pmrotule

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2 Comments

serkan Over a year ago

in this case ("gök" == "GÖK".toLowerCase().replace(/[^ -~]/g,'')) return false.

pmrotule Over a year ago

@serdem420 I edited my answer to make it works with all special characters like in your example.

Ismael Miguel · Accepted Answer · 2016-06-13 13:44:02Z

3

The problem is that your character İ is composed by 2 characters.

You have the I and then the 'dot' at the top (UTF-8 decimal code: 775).

Try this:

"HİNDİ".toLocaleLowerCase().split('').map((_,v)=>console.log(_.charCodeAt(0)))

Compare it with this:

"hindi".toLocaleLowerCase().split('').map((_,v)=>console.log(_.charCodeAt(0)))

answered Jun 13, 2016 at 13:44

Ismael Miguel

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2 Comments

serkan Over a year ago

Thanks for the answer, that makes sense. Is there any way to produce "true" for this kind of situations?

Ismael Miguel Over a year ago

Yes, there is. But, it isn't a nice solution. You can remove every diacritic mark from your string and compare it.

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