JavaScript append string
There are the following ways to append a string in JavaScript.
- Using the + operator
- Using template literals
- Using the concat() method
- Use the join() method
Method 1: Using the + operator
The + or concate operator is used to concatenate two strings. If the left-hand side of the + operator is a string, JavaScript will coerce the right-hand side into a string. In JavaScript, the “+” concatenation creates a new String object.
Example
let str = "Maeve: ";
str += "Wiley";
console.log(str);
Output
Maeve: Wiley
You can see that we have appended a “Wiley” string to the “Maeve” string.
The + and += operators are fast in modern JavaScript engines, so we used them to append the string.
Method 2: Using template literals
Template literals are string literals producing enclosed expressions. You can use multi-line strings and string interpolation features with them. For example, this is the output of the following string before template strings.
Example
let fn = "Krunal"
let country = "India"
console.log("Hi, I'm " + fn + " and I'm from " + country);
Output
Hi, I'm Krunal and I'm from India
You can see that the code is not easily readable, and you can make mistakes if you are not careful. It is a mess and cumbersome.
To resolve this issue, we can use the template literals, which makes things super easy.
let fn = "Krunal"
let country = "India"
console.log(`Hi, I'm ${fn} and I'm from ${country}`);
Output
Hi, I'm Krunal and I'm from India
Template literals can contain placeholders indicated by the dollar sign and curly braces (${expression}).
The expressions in the placeholders and the text between the backticks (` `) get passed to a function.
It returns the same output as the + operator, but it is more readable and more understandable.
Method 3: Using the concat() method
The string concat() is a built-in JavaScript method that takes one or more parameters and returns the modified string. You can use the concat() method to append or join the strings.
Example
const dt1 = "Otis";
const dt2 = dt1.concat(" ", "Milburne");
console.log(dt1);
console.log(dt2);
Output
Otis
Otis Milburne
As you can see that we have appended a “Milburne” string to the “Otis” string using the string.concat() method.
One downside of using string.concat() method is that the input must be a string. If the input parameter is null and you call the concat() function, it will return a TypeError.
const dt1 = null;
const dt2 = dt1.concat(" ", "Milburne");
console.log(dt1);
console.log(dt2);
Output
/Users/krunal/Desktop/code/node-examples/es/app.js:10
const dt2 = dt1.concat(" ", "Milburne");
^
TypeError: Cannot read property 'concat' of null
In the output, we get TypeError: Cannot read property ‘concat’ of null. The concat() method is rarely used because it has more error cases than the + operator.
The best use case of the concat() method is to call it on an empty string.
console.log(''.concat('Data', ' ', 'Science'));
Output
Data Science
Method 4: Using the join() method
The array join() is a built-in method that combines the array items and returns a string. A specified separator will separate the elements. The default separator is a comma (,). If you are working with an array, adding additional strings is beneficial.
Example
const spain = "Hola";
const belgium = "Hello";
const switzerland = ['Other winners are ', spain, belgium];
const italy = "kem chho";
switzerland.push(italy);
console.log(switzerland.join(' '));
Output
Other winners are Hola Hello kem chho
We have appended the array elements and converted them into a string using the join() method.
That’s it.

Niva Shah is a Software Engineer with over eight years of experience. She has developed a strong foundation in computer science principles and a passion for problem-solving.