Javascript什么是“'+ ​​aStringVarible +'”（双引号加单引号）呢？

Question

I saw this line of code from an online course:

photoHtml += '<a href="' + photo.link + '">';

Here, "photo" is an object, and photo.link is actually a url.

But it is my first time seeing people use "' together (I am new to javascript), so I am not sure what this does. My guessing is that it is a way to add quotations to a variable? Because if we directly put quotes around the variable photo.link, then it would not work as a variable, eg "photo.link"?

In python, I would use '"' + photo.link + '"' to deal with the case. So does "' + photo.link + '" do the same job here in javascript?

Thank you in advance! I know it is really amateur, but I tried to search on google, and did not find desired answers.

Answer 1

You can define string literals either like this 'a string' or "a string" . Both allow the other kind of character to be included without an escape character: '"hello" world' is a string containing "hello" world .

Answer 2

The valid HTML produced by this will be something like

<a href="http://something.com/">

Notice that the quotes " delimit the link url .

Now, in JavaScript, regardless of the content of a string, the string in photoHTML is delimited by the quotes ' . Thus, if you want your url to be a variable, you must somehow place it such that the produced html looks like this:

<a href="photo.link">

Where you want to replace the text photo.link with your actual link. This is achieved by:

photoHtml += '<a href="' + photo.link + '">';

where the " quotes delimit the url in the html and the ' quotes delimit the string in the JavaScript .

Answer 3

The " has nothing to do with it the concatenation. The " is for the attribute that is being rendered.

<a href="thelink">
        ^       ^

Answer 4

The value of the href attribute has to be enclosed by quotation marks. It doesn't matter if it's a ' single or a " double quotation mark.

In your example the ' marks beginning and end of the javascript expression (string concatenation) while the " refers to the html attribute href and is part of the string itself.