问题
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>
I thought, that given the above, these would be equivalent:
element(by.css('#eId'));
and
element($('#eId'));
However, the first one works and the second doesn't. Why, what's the difference between the three?
The docs are of little help. They seem to imply that "$" 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.
Anyway, that's a lot of text for "What are the differences between the three (by.css, $, and $$)?"
回答1:
$ and $$ are just convenient shortcuts.
$("selector")
is an alternative for element(by.css("selector"))
.
$$("selector")
is an alternative for element.all(by.css("selector"))
.
FYI, quote from the source code:
ElementFinder.prototype.$ = function(selector) {
return this.element(webdriver.By.css(selector));
};
ElementArrayFinder.prototype.$$ = function(selector) {
return this.all(webdriver.By.css(selector));
};
And the actual commit that initially made it happen.
来源:https://stackoverflow.com/questions/31881583/protractor-by-css-vs-dollar-sign-vs-bling-bling