regular expression find end of string

Question

I have troubles with a regular expression.

I want to replace all ocurrences of myData=xxxx& xxxx can change, but always ends with &, except the last ocurrence, when it is myData=xxx.

var data = "the text myData=data1& and &myData=otherData& and end myData=endofstring"
data.replace(/myData=.*?&/g,'newData');

it returns :

the text newData and &newData and end myData=endofstring

which is correct, but how can I detect the last one?

Answer 1

Two things:

1. You need to assign the result of replace somewhere, which you're not doing in your question's code

2. You can use an alternation (|) to match either & or end of string

So:

    var data = "the text myData=data1& and &myData=otherData& and end myData=endofstring"
    data = data.replace(/myData=.*?(?:&|$)/g,'newData');
//  ^^^^^^^-- 1                    ^^^^^^^-- 2
console.log(data);

Note the use of a non-capturing group ((?:...)), to limit the scope of the alternation.