等待元素渲染完毕执行和sleep

// 延迟执行
function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

// 等待元素渲染完成后执行
function whenElementExist(selector) {
    return new Promise(resolve => {
        const checkForElement = () => {
            let element = null;
            if (typeof selector === 'function') {
                element = selector();
            } else {
                element = document.querySelector(selector);
            }
            if (element) {
                resolve(element);
            } else {
                requestAnimationFrame(checkForElement);
            }
        };
        checkForElement();
    });
}

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