JS: Count Chars in String 📜

By Xah Lee. Date: . Last updated: .

Problem

see JS: String Index and Code Unit

Quick solution

console.log(Array.from("🌞🦋").length);
// 2

Memory efficient solution

/*
xah_string_char_count(zstr)
return number of chars in string zstr.

URL http://xahlee.info/js/js_string_real_length.html
Created: 2018-06-17
Version: 2026-01-13
*/

const xah_string_char_count = (zstr) => {
 let xtotal = 0;
 for (let _ of zstr) xtotal++;
 return xtotal;
};

// s------------------------------

// test
console.log(xah_string_char_count("🦋"));
// 1

Test speed and memory

// file name: bench.js

const fa = (zstr) => ([...zstr].length);
const fb = (zstr) => {
 let xtotal = 0;
 for (let _ of zstr) xtotal++;
 return xtotal;
};

/*
fgenStr(xcharArray, xcount)
returns a array of length xcount.
elements are randomly selected from array xcharArray.
*/
const fgenStr = (xcharArray, xcount) => {
 const xlen = xcharArray.length;
 return (Array.from(Array(xcount), () => xcharArray[Math.floor(Math.random() * xlen)]));
};

const xbigstring = fgenStr(["a", "b", "⭐", "🦋"], 10 ** 4).join("");

console.log("string length is ", xbigstring.length);
console.log("fa result is", fa(xbigstring));
console.log("fb result is", fb(xbigstring));

// s------------------------------

Deno.bench("test fa", () => {
 fa(xbigstring);
});

Deno.bench("test fb", () => {
 fb(xbigstring);
});
js speed unicode string char count 2026-01-15 1b5a1
js speed unicode string char count 2026-01-15 1b5a1