Eğitim / Kodlama 8 Mayıs 2024

JavaScript Concatenate Strings – How JS String Concatenation Works

When coding in JavaScript, you may need to combine multiple strings to create a new, longer string. This operation is known as concatenation.

In this article, you will learn five ways to concatenate strings in JavaScript.

How to Concatenate Strings in JavaScript Using the + Operator

The + operator isn’t used only for performing addition but also for concatenating strings.

Let’s take the following example:

let greeting = "Hello";
let name = "John";

let result = greeting + name;

console.log(result); 

In the code above, I created two variables named greeting and name, and stored the string values Hello and John, respectively.

I also created another variable named result and stored the result of concatenating greeting and name using the + operator.

Finally, I used console.log() to output the result to the console.

If you look closely at the output, HelloJohn, you will notice that there is no space between Hello and John. The result of joining the two strings, Hello and John, will be a new single string, HelloJohn.

When concatenating strings with the + operator, you have to remember to add spaces between the strings, or you will end up with unexpected output:

let greeting = "Hello";
let name = "John";

let result = greeting + " " + name;

console.log(result); 

So, although the + operator is a convenient approach for basic string concatenation in JavaScript, you have to be mindful of manually separating the strings, which can lead to errors when performing more complex string concatenation.

How to Concatenate Strings in JavaScript Using the += Operator

The += operator is used when you want to add a string to an existing string.

Let’s take the following example:

let name = "John ";

name += "Doe";

console.log(name); 

In the example above, I created a variable name and stored the string value John with a space at the end. Note that when using the += operator, you have to add spaces to separate the strings, similar to when using the + operator.

Then, I added the string Doe to the name variable. After this operation, the name variable will contain the string John Doe.

The += operator takes the original value of the variable name, John, adds the value Doe and assigns the result back to the variable.

You can think of the line name += "Doe"; as a shorthand for name = name + "Doe".

How to Concatenate Strings in JavaScript Using Template Literals

As you saw earlier, the + operator is convenient for basic string concatenation. However, code can become hard to read or lead to errors when performing more complex string concatenation.

Template literals offer a more readable alternative and make working with strings easier.

Template literals use backticks (`) to enclose a string instead of single or double quotes. Inside the backticks, you can insert variables or expressions directly into strings using ${}.

Let’s revisit the code for concatenating strings using the + operator:

let greeting = "Hello";
let name = "John";

let result = greeting + " " + name;

console.log(result); 

Here is how you would rewrite the code using template literals:

let greeting = "Hello";
let name = "John";

let result = `${greeting} ${name}`;

console.log(result); 

The ${greeting} and ${name} are like placeholders that get replaced with the actual values of the variables. ${greeting} embeds the value of the variable greeting into the string, and ${name} embeds the value of the variable name.

While both code examples achieve the same output, the code using template literals is more readable and concise compared to the code using the + operator.

How to Concatenate Strings in JavaScript Using the concat() Method

You can also use the built-in concat() method to concatenate two or more strings in JavaScript.

The general syntax for the concat() method looks something similar to the following:

string.concat(string1, string2, ..., stringN)

You can call the concat() method on a string and pass the string(s) you want to concatenate as arguments inside the parentheses. When you pass multiple strings as arguments, you separate each string with a comma.

Note that the concat() method doesn’t change the original string. Instead, it returns a new concatenated string.

Let’s see an example of the concat() method in action:

let greeting = "Hello";
let name = "John";

let result = greeting.concat(name);

console.log(result); 
console.log(greeting);





In the code above, the concat() method is called on the initial string variable name, and the greeting string variable is passed as an argument.

This creates a new string, Hello John, where name is added to the end of greeting. The string in the greeting variable doesn’t change.

How to Concatenate Strings in JavaScript Using the join() Method

Lastly, you can concatenate strings using the built-in join() method.

The general syntax for the join() method looks something like the following:

array.join(separator);

The join() method comes in handy when working with arrays of strings, as it combines all array elements into a single string separated by a separator you specify. When you don’t specify a separator, a comma is used by default.

Let’s take the following example:

let programmingLanguages = ["JavaScript", "Java", "Python"];

let result = programmingLanguages.join(", ");

console.log(result); 

In the example above, I first created an array called programmingLanguages containing three strings: JavaScript, Java, and Python.

Next, I called the join() method on programmingLanguages to concatenate all array elements into a single string and used a comma followed by a space, , , as the separator. Then, I stored the result in a new variable called result.

The array elements JavaScript, Java, and Python are joined together with a comma and a space between each element, resulting in the string JavaScript, Java, Python.

Conclusion

In this article, you learned five ways of concatenating strings in JavaScript.

To summarise:

  • The + operator is useful for performing basic string concatenation, but it can become less readable when performing more complex concatenations.

  • The += operator comes in handy when you want to add a string to an existing string and modify the original string.

  • Template literals allow you to embed variables directly within a string and provide a readable and concise syntax.

  • The concat() method is useful when you want to concatenate strings but don’t want to modify the existing strings.

  • The join() method allows you to concatenate an array of strings into a single string, with an optional separator between each array element.

Thanks for reading, and happy coding!

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