Why do i need to add /g when using string replace in Javascript?

Question

Why is the \'/g\' required when using string replace in JavaScript?

e.g. var myString = myString.replace(/%0D%0A/g,\"
\");

Answer 1

The "g" that you are talking about at the end of your regular expression is called a "modifier". The "g" represents the "global modifier". This means that your replace will replace all copies of the matched string with the replacement string you provide.

A list of useful modifiers:

1. g - Global replace. Replace all instances of the matched string in the provided text.
2. i - Case insensitive replace. Replace all instances of the matched string, ignoring differences in case.
3. m - Multi-line replace. The regular expression should be tested for matches over multiple lines.

You can combine modifiers, such as g and i together, to get a global case insensitive search.

Examples:

//Replace the first lowercase t we find with X
'This is sparta!'.replace(/t/,'X');
//result: 'This is sparXa!'

//Replace the first letter t (upper or lower) with X
'This is sparta!'.replace(/t/i, 'X');
//result: 'Xhis is sparta!'

//Replace all the Ts in the text (upper or lower) with X
'This is sparta!'.replace(/t/gi, 'X' );
//result: 'Xhis is sparXa!'

For more information see the JavaScript RegExp Object Reference at the w3schools.