Syntax Highlighter.js

function recolor() {
    let bf = document.querySelectorAll(".brainfuck");
    bf.forEach((code) => {
        var start = code.selectionStart;
    var end = code.selectionEnd;
        // console.log(start);

        let curCode = code.innerText;
        let newCode = "";

        let lastCode = '';
        for (let i = 0; i < curCode.length; i++) {
            let c = curCode.charAt(i);
            let codeType = 'comment';

            switch(c) {
                case '>':
                case '<':
                    codeType = 'shift';
                    break;

                case '.':
                case ',':
                    codeType = 'io';
                    break;

                case '[':
                case ']':
                    codeType = 'loop';
                    break;

                case '+':
                case '-':
                    codeType = 'edit';
                    break;
            }

            if (codeType != lastCode) {
                if (i != 0) {
                    newCode += '</span>';
                }
                newCode += `<span class='${codeType}'>`;
            }
            newCode += c;
            lastCode = codeType;
        }
        newCode += "</span>";
        code.innerHTML = newCode;
    });
}

window.onload = () => {
    recolor();
    setInterval(()=> {
        recolor();
    }, 50);
}