Brainfuck interpreter in js

brainFuck.js

const brainFuckInput = () => {
    const input = prompt('输入一个字符或不输入。\n若输入多个字符，只有输入的第一个字符有效。');
    if (input) return input.codePointAt();
    else return 0;
};

const brainFuckOutput = (value) => {
    console.info(String.fromCodePoint(value));
};

const brainFuck = (code, i=brainFuckInput, o=brainFuckOutput, block=512) => {
    let buffer = new Uint8Array(block);
    let cursor = 0;
    const callStack = [];
    for (let index = 0; index < code.length; index++)
    switch(code[index]) {
        case '>': {
            if (++cursor >= buffer.length) {
                const newBuffer = new Uint8Array(buffer.length + block);
                newBuffer.set(buffer);
                buffer = newBuffer;
            }
            break;
        }
        case '<': --cursor; break;
        case '+': ++buffer[cursor]; break;
        case '-': --buffer[cursor]; break;
        case '.': o(buffer[cursor]); break;
        case ',': buffer[cursor] = i(); break;
        case '[': callStack.unshift(index); break;
        case ']': {
            if (buffer[cursor]) 
                index = callStack[0];
            else 
                callStack.shift();
            break;
        }
    }
};

brainFuckAsync.js

/**
 * BrainFuck DOM Input
 * @param {HTMLInputElement} element target input element
 */
const brainFuckDOMInput = (element = document.querySelector('input')) => () => {
    return new Promise(r => {
        element.onkeydown = ({key, ctrlKey}) => {
            if (ctrlKey && key.toLowerCase() == 'c')
                return r(0);
            if (key === 'Enter')
                return r(10);
            if (key.length === 1)
                return key.codePointAt();
        };
    });
};

/**
 * BrainFuck DOM Output
 * @param {Element} element output element
 */
const brainFuckDOMOutput = (element = document.body.lastElementChild) => (value) => {
    if (value <= 0) return;
    value = String.fromCodePoint(value);
    if (element instanceof HTMLInputElement)
        element.value += value;
    else
        element.innerText += value;
};

/**
 * Async Brainfuck interpreter
 * @param code target BrainFuck code
 * @param i async BrainFuck input handler
 * @param o BrainFuck output handler
 */
const brainFuckAsync = async(code, i=brainFuckDOMInput(), o=brainFuckDOMOutput(), block=512) => {
    let buffer = new Uint8Array(block);
    let cursor = 0;
    const callStack = [];
    for (let index = 0; index < code.length; index++)
    switch(code[index]) {
        case '>': {
            if (++cursor >= buffer.length) {
                const newBuffer = new Uint8Array(buffer.length + block);
                newBuffer.set(buffer);
                buffer = newBuffer;
            }
            break;
        }
        case '<': --cursor; break;
        case '+': ++buffer[cursor]; break;
        case '-': --buffer[cursor]; break;
        case '.': o(buffer[cursor]); break;
        case ',': buffer[cursor] = await i(); break;
        case '[': callStack.unshift(index); break;
        case ']': {
            if (buffer[cursor]) 
                index = callStack[0];
            else 
                callStack.shift();
            break;
        }
    }
};