why same regex expression gives two different results?

Question

Hi I have two typescript snippet . both wants to achieve the same . however console.log prints different value. any idea what is wrong? why the code 2 prints false .

var regex1 = new RegExp(/^FEDEX /)
var messagePrefix = "FEDEX "
console.log(regex1.test(messagePrefix)); // this prints true 

let messageControlValue:string = "FEDEX "
let regex2:RegExp = new RegExp(/^messageControlValue/);
console.log(regex2.test(messagePrefix)); // this prints false

really appreciatiate any help thanks

Because `messageControlValue` in `new RegExp(/^messageControlValue/)` is a `messageControlValue` string, not a `messageControlValue` variable. You meant to use `new RegExp("^" + messageControlValue)` — Wiktor Stribiżew, Jul 31 '19 at 13:39

score 3 · Accepted Answer · answered Jul 31 '19 at 13:39

3

Because in the second one you're literally testing for the string messageControlValue. Construct it like so:

let regex2: RegExp = new RegExp(`^${messageControlValue}`);

Or:

let regex2: RegExp = new RegExp("^" + messageControlValue);

answered Jul 31 '19 at 13:39

Jack Bashford

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excellant thank you – knowledgeseeker Jul 31 '19 at 14:06
No problem @knowledgeseeker, always glad to help. – Jack Bashford Jul 31 '19 at 14:06
could you help me with this https://stackoverflow.com/questions/57290784/why-i-am-not-able-to-make-the-text-area-partially-non-editable-in-angular-5-and – knowledgeseeker Jul 31 '19 at 14:27

why same regex expression gives two different results?

1 Answers1