如何计算具有特定类名的元素的数量? [英] How to count the number of elements with a particular class name?

问题描述

如何使用夜表计数具有特定类名称的元素的数量?

How do I count the number of elements with a particular class name using nightwatch?

例如，我想计算页面上类名称为"sample"的元素的数量，并检查该数量是否大于8.如何使用夜表来做到这一点?

For example, I want to count the number of elements with class name "sample" on the page and check that the number if greater than 8. How can I do that using nightwatch?

推荐答案

假设您的页面包含此标记:

Assuming your page includes this markup:

<ul id="names">
    <li>Stephanie</li>
    <li>Luke</li>
    <li>Marina</li>
</ul>

您可以执行以下操作:

module.exports = {
    'Example test': browser => {
        browser.url(browser.launchUrl);
        browser.elements('css selector', '#names li', result => {
            const numElements = result.value.length;
            console.log(numElements);
        });
    }
}

请记住，您不能在该回调之外使用numElements.从回调中返回它无济于事:browser.elements忽略返回值.在回调之前初始化numElements并在其内部设置 值对回调也无济于事:回调可能会运行得更晚.

Just bear in mind that you can't use numElements outside of that callback. Returning it from the callback won't help: browser.elements ignores the return value. Initializing numElements before the callback and setting its value inside the callback won't help either: the callback might be run much later.

如果您确实需要在回调之外使用该值，则需要使用Promise:

If you really need to use that value outside of the callback, you'll need to use a Promise:

module.exports = {
    'Example test': browser => {
        browser.url(browser.launchUrl);

        const numElementsPromise = new Promise(resolve => {
            browser.elements('css selector', '#names li', result => {
                resolve(result.value.length);
            });
        });

        numElementsPromise.then(numElements => {
            console.log(numElements);
        });
    }
}

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