JavaScript String replace vs replaceAll

Question

ECMAScript 2021 has added a new String function replaceAll . A long time ago in a galaxy not so far away, people used split + join or regular expressions to replace all occurences of a string .

I created the following example to compare the new method to the old ones. While I could see some differences in the first case, for example I can't use replacement patterns with split + join or I need to escape special chars with RegExp(str,"g") , I can't see any difference in the second case.

What are the differences between the new method and the old ones (behaviour difference, performance, browser compatibility...)?

 const source = "abcdefabcdef"; const str1 = "abc", str2 = "xyz"; const reg1 = /abc/g, reg2 = "xyz"; //Case 1: When we want to replace a string by another console.log(source.split(str1).join(str2)); console.log(source.replace(new RegExp(str1,"g"),str2)); //versus console.log(source.replaceAll(str1,str2)); //Case 2: When we want to use a regular expression console.log(source.replace(reg1,reg2)); //versus console.log(source.replaceAll(reg1,reg2)); //Result = "xyzdefxyzdef"

Answer 1

From gleaning the documentation for replaceAll , we find the following tidbits:

const newStr = str.replaceAll(regexp|substr, newSubstr|function)

Note: When using a regexp you have to set the global ("g") flag; otherwise, it will throw a TypeError: "replaceAll must be called with a global RegExp".

In other words, when calling replaceAll with a regex literal or RegExp , it must use the global flag. So, there doesn't seem to be much gained by calling replaceAll versus just using the current replace . However, one difference with replaceAll is that when passing it a string, it will automatically do a global replacement. This is where you might save yourself a bit of typing, by not having to enter a global flag.