量角器“by.css()"vs“$()"美元符号与“$$()"'亮闪闪'

2022-01-16 00:00:00 selenium testing angularjs protractor javascript

我不太明白 $ 和 $$ 命令的用途.我认为它们只是by.css"的替代品，但为什么要使用 $$?

I don't really understand what the $ and $$ commands are for. I thought they are just a replacement for 'by.css' but why the $$? 

<element id = "eId"></element>

我认为，鉴于上述情况，这些将是等效的:

I thought, that given the above, these would be equivalent:

element(by.css('#eId'));

和

element($('#eId'));

但是，第一个有效，第二个无效.为什么，这三者有什么区别?

However, the first one works and the second doesn't. Why, what's the difference between the three?

docs 帮助不大.他们似乎暗示$"仅用于链接，例如element(by.css('#eId')).element($('#childId')); 或选择第一个元素，然后选择第一个元素内的第二个元素."但是，我已经看到使用 $ 来选择第一个元素的示例.

The docs are of little help. They seem to imply that "$" is for chaining only, e.g. element(by.css('#eId')).element($('#childId')); or "Select the first element, and then select the second element within the first element.' However, I have seen examples with $ being used to select the first element.

不管怎样，这三个(by.css、$ 和 $$)之间有什么区别?"的文字很多.

Anyway, that's a lot of text for "What are the differences between the three (by.css, $, and $$)?"

推荐答案

$ 和 $$ 只是方便的快捷方式.

$ and $$ are just convenient shortcuts.

$("selector") 是 element(by.css("selector")) 的替代品.

$$("selector") 是 element.all(by.css("selector")) 的替代品.

仅供参考，引用自 源代码:p>

FYI, quote from the source code:

ElementFinder.prototype.$ = function(selector) {
  return this.element(webdriver.By.css(selector));
};

ElementArrayFinder.prototype.$$ = function(selector) {
  return this.all(webdriver.By.css(selector));
};

以及最初实现它的实际提交.

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