JavaScript String Concatenation
To combine, or join text strings together.
concat()
TheĀ concat()
method concatenates, or appends string(s) to the calling string and returns the result as a new string.
const str = 'Fire'.concat('trucks');
console.log(str); // 'Firetrucks'
You can concatenate multiple parameters:
const originalStr = 'Fire';
const str1 = 'trucks';
const str2 = ' ';
const str3 = 'are the best!';
const str = originalStr.concat(str1, str2, str3);
console.log(str); // 'Firetrucks are the best!'
The same can be done with an array of arguments and the rest parameter, if you don't know how many parameters there will be:
let coolVehicles = ['Firetrucks', ' & ', 'Ambulances', '!'];
let str = ''.concat(...coolVehicles);
console.log(str); // 'Firetrucks & Ambulances!'
It's strongly recommended that the assignment operators (+
, +=
) are used instead of the concat() method because of performance.
+ operator
The +
operator returns a new string:
const str1 = 'Now I know how to';
const str2 = 'concatenate!';
const str = str1 + ' ' + str2;
console.log(str); // 'Now I know how to concatenate!'
+= operator
The +=
operator modifies the original string:
let str = 'Now I know how to';
str += ' ';
str += 'concatenate!';
console.log(str); // 'Now I know how to concatenate!'
Template Literals
Recognized by the backticksĀ `
allowing embedded expressions called substitutions.
const str1 = 'Now I know how to';
const str2 = 'concatenate';
const str = `${str1} correctly ${str2} like a pro!`;
console.log(str); // 'Now I know how to correctly concatenate like a pro!'