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Convert multiline string to single line string in JavaScript

To convert multiline string to single line string, call the string replace() method. You have to pass a regular expression /\n/g as the first argument, and an empty string "" or a space " " as the second argument to the replace() method.

The following JavaScript code converts multiline string to single line string:

let str = `This
is
a
Multiline
String.`;
str = str.replace(/\n/g, ' ');
console.log(str);

Output

The g flag in the regular expression replaces all the occurrences of \n newline characters with a space.

You can also convert a multiline string created using the + operator or \ operator to a single line string. The following JavaScript code shows you how to achieve this:

let str1 = 'This\n' +
'is\n' +
'a\n' +
'Multiline\n' +
'String.';

let str2 = 'This\n \
is\n \
a\n \
Multiline\n \
String.';

str1 = str1.replace(/\n/g, ' ');
str2 = str2.replace(/\n/g, '');
console.log(str1);
console.log(str2);