How can the '+' symbol affect the function "url(" + imageUrl + ")"?

I was looking at some jQuery code on a website and came across a line that confused me. What exactly does the + sign and spaces do in "url(" + imageUrl + ")"?

I am new to jQuery and JavaScript.

<!DOCTYPE html>
<html lang="en">
<head>
<title>jQuery Setting background-image CSS Property</title>
<style>
    .box{
        width: 500px;
        height: 300px;
        border: 5px solid #333;
    }
</style>
<script src="https://code.jquery.com/jquery-3.5.1.min.js"></script>
<script>
$(document).ready(function(){
    // Set background image of a div on click of the button
    $("button").click(function(){
        var imageUrl = "images/sky.jpg";
        $(".box").css("background-image", "url(" + imageUrl + ")");
    });    
});
</script>
</head>
<body>
    <div class="box"></div>
    <p><button type="button">Set Background Image</button></p>
</body>
</html><!DOCTYPE html>

Answer №1

When working with Javascript, you can join strings together using the + operator.

For instance,

let string1 = Hello;
let string2 = World;
let fullString = string1 + string2; // Result: HelloWorld.

Essentially, your code is simply combining the imageUrl with the url() function.

Ultimately, the outcome will be something like url("images/sky.jpg").

Answer №2

The plus sign (+) in JavaScript serves various purposes depending on the situation in which it is used. The function of the plus operator is determined by its surroundings.

When used in a numerical context, the plus operator is employed for addition

1 + 2 // 3

On the other hand, in a string context, it is utilized for concatenation
'1' + '2' // '12'
1 + '2' // '12'

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