The concat() method combines the text of two or more strings and returns a new string.

Syntax

str.concat(string2[,..., stringN]);

string2...string_N_ The strings which are to be concatenated to this String.

The concat() method combines the text of two or more strings and returns the concatenated string. It does not modify the original strings.

Concatenating strings

var str1 = "Hello";
var str2 = "World";
console.log(str1.concat(str2));
// Console will output: HelloWorld

var str2 = "Hello, ";
console.log(str2.concat(" Welcome ", "to FCC."));
// Console will output: Hello, Welcome to FCC.

Source MDN