You can take advantage of Template Literals and use this syntax:

`String text ${expression}`

Template literals are enclosed by the back-tick (` `) (grave accent) instead of double or single quotes.

This feature has been introduced in ES2015 (ES6).

Example

var a = 5;
var b = 10;
console.log(`Fifteen is ${a + b}.`);
// "Fifteen is 15.

How neat is that?

Bonus:

It also allows for multi-line strings in javascript without escaping, which is great for templates:

return `
    <div class="${foo}">
         ...
    </div>
`;

Browser support:

As this syntax is not supported by older browsers (mostly Internet Explorer), you may want to use Babel/Webpack to transpile your code into ES5 to ensure it will run everywhere.

Side note:

Starting from IE8+ you can use basic string formatting inside console.log:

console.log('%s is %d.', 'Fifteen', 15);
// Fifteen is 15.

Introduced in ES6 as "template strings"

MDN docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals

const name = "Nick"
const greeting = `Hello ${name}`  // "Hello Nick"

As with most languages that don't have sigals, you can't perform interpolation, you have to concatenate multiple strings.

"foo" + "bar" + "baz"
"foo" + string_var + "baz"
"+=" + string_var + "px"