JavaScript Replace Characters in a String

To replace characters in a string in JavaScript, we can use the string.replace() methods,

Assign to a new variable

One thing to keep in mind is that the replace method does not change the original string. So in order to get the new string after some of its characters are replaced, we need to assign the operation to a new variable or even itself.

var str = "a b c a b c";
str.replace("a","");
console.log(str);
//a b c a b c which is the same as before.

var newStr = str.replace("a","");
console.log(newStr);
//b c a b c. The first a is gone.

str = str.replace("a","");
console.log(str);
//b c a b c. Assign to itself wokks, too.

Differences between g and m in Regular Expression

Actually, you can just use g not gm in the regular expression if you want to replace multiple characters in a string. Here \n means a line break in the string.

var str = "a b c \na b c";
str = str.replace(/a/g,"");

console.log(str);
/*
    b c
    b c
*/

str = str.replace(/a/gm,"");
// or str = str.replace(/a/mg,"");
console.log(str);
/*
    b c
    b c
*/

Examples

Replacing all slashes

var str = "a/b/c/d";
str = str.replace(/\//g,"");

console.log(str);
// abcd

Replacing all backslashs

var str = "a\\b";
str = str.replace(/\\/g,"");

console.log(str);
// ab

Replacing all line breaks

var str = "a\nb\nc";
str = str.replace(/\n/g,"");

console.log(str);
// abc