Question

I have a string with multiple commas, and the string replace method will only change the first one:

var mystring = "this,is,a,test"
mystring.replace(",","newchar", -1)

Result: "thisnewcharis,a,test"

The documentation indicates that the default replaces all, and that “-1” also indicates to replace all, but it is unsuccessful. Any thoughts?

Answer 1

The third parameter of the String.prototype.replace() function was never defined as a standard, so most browsers simply do not implement it. It was eventually removed and replaced with String.prototype.replaceAll() (see below).

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Modern solution (2022)

Use String.prototype.replaceAll(). It is now supported in all browsers and NodeJS.

var myStr = "this,is,a,test";
var newStr = myStr.replaceAll(",", "-");

console.log( newStr );  // "this-is-a-test"

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The old way is to use a regular expression with g (global) flag

var myStr = "this,is,a,test";
var newStr = myStr.replace(/,/g, "-");

console.log( newStr );  // "this-is-a-test"

Have issues with regular expressions?

It is important to note, that regular expressions use special characters that need to be escaped. For example, if you need to escape a dot (.) character, you should use /\./ literal, as in the regex syntax a dot matches any single character (except line terminators).

If you need to pass a variable as a replacement string, instead of using regex literal you may create a RegExp object and pass a string as its first argument. The usual escape rules (preceding special characters with \ when included in a string) will be necessary.

function escapeRegex(str) {
    return str.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"); // $& means the whole matched string
}

var myStr = "this.is.a.test";
var reStr = escapeRegex(".");
var newStr = myStr.replace(new RegExp(reStr, "g"), "-");

console.log( newStr );  // "this-is-a-test"