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Concatenating variables and strings in React

Is there a way to incorporate React’s curly brace notation and an href tag? Say we have the following value in the state:

{this.state.id}

and the following HTML attributes on a tag:

href="#demo1"
id="demo1"

Is there a way I can add the id state to the HTML attribute to get something like this:

href={"#demo + {this.state.id}"}

Which will yield:

#demo1

Answer

You’re almost correct, just misplaced a few quotes. Wrapping the whole thing in regular quotes will literally give you the string #demo + {this.state.id} – you need to indicate which are variables and which are string literals. Since anything inside {} is an inline JSX expression, you can do:

href={"#demo" + this.state.id}

This will use the string literal #demo and concatenate it to the value of this.state.id. This can then be applied to all strings. Consider this:

var text = "world";

And this:

{"Hello " + text + " Andrew"}

This will yield:

Hello world Andrew 

You can also use ES6 string interpolation/template literals with ` (backticks) and ${expr} (interpolated expression), which is closer to what you seem to be trying to do:

href={`#demo${this.state.id}`}

This will basically substitute the value of this.state.id, concatenating it to #demo. It is equivalent to doing: "#demo" + this.state.id.