const timeLimit = 1.0;
timeout = null;
function halt() {
    done = true;
}
function loop() {
    if (timeout === null) {
        timeout = setTimeout(halt, timeLimit * 1000);
        done = false;
    }
    if (done) {
        console.log("Halted.");
        timeout = null;
    } else {
        console.log("Running...");
        setTimeout(loop, 0);
    }
}
loop();

function run(prog, inp) {
    while(prog!='') { ... }
}

function onClick() {
    run();
}

async function run(prog, inp) {
    while(prog!='') {
        ...

        await new Promise(r => setTimeout(r, 0));
    }
}

function onClick() {
    run();
}

async function run(prog, inp) {
    while(prog!='') {
        while (xyz) {
            ...

            await new Promise(r => setTimeout(r, 0));
        }

        while (xyz2) {
            ...

            await new Promise(r => setTimeout(r, 0));
        }

        ...

        await new Promise(r => setTimeout(r, 0));
    }
}

function onClick() {
    run();
}