How to interpolate variables in strings in JavaScript, without concatenation?

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.

Prior to Firefox 34 / Chrome 41 / Safari 9 / Microsoft Edge, nope, that was not possible in javascript. You would have to resort to:

var hello = "foo";var my_string = "I pity the " + hello;

Prior to Firefox 34 / Chrome 41 / Safari 9 / Microsoft Edge, no. Although you could try sprintf for JavaScript to get halfway there:

var hello = "foo";var my_string = sprintf("I pity the %s", hello);