错误类型错误：无法读取 null 的属性“1”

Question

I am trying to parse card data that is passed through a card reader, however, I am getting an error in regards to the regex. I understand it means that this.match is null but I am not sure why it is null. Any suggestions? (Using Angular 9)

    CardData: string;
    CardPattern = new RegExp("^\%B(\d+)\^(\w+)\/(\w+)\^\d+\?;\d+=(\d\d)(\d\d)\d+$");
    CardNumber: string;
    FirstName: string;
    LastName: string;
    ExpData: string;
    match: RegExpExecArray;

    constructor(private snackbar: SnackBar) {
    }

    ngOnInit() {
        // getaCardData();
        this.CardData = "%B6545461234613451^DOE/JOHN^00000000000000000000000?;6545461234613451=984651465116111?"

        this.match = this.CardPattern.exec(this.CardData);

        this.CardNumber = this.match[1]
        this.FirstName = this.match[3];
        this.LastName = this.match[2];
        this.ExpData = this.match[5] + "/" +this.match[4];

        console.log(this.CardNumber);
    }

Answer 1

Your pattern does not match because you have an additional character ? at the end of your string: this.CardData = %B6545461234613451^DOE/JOHN^00000000000000000000000?;6545461234613451=984651465116111?"

Replace it with:

this.CardData = "%B6545461234613451^DOE/JOHN^00000000000000000000000?;6545461234613451=984651465116111"

or change your pattern instead with: ^\\%B(\\d+)\\^(\\w+)\\/(\\w+)\\^\\d+\\?;\\d+=(\\d\\d)(\\d\\d)\\d+\\?$

Update: Added working code snippet for you reference! Try adding flags and it should work.

 const regex = new RegExp(/^\\%B(\\d+)\\^(\\w+)\\/(\\w+)\\^\\d+\\?;\\d+=(\\d\\d)(\\d\\d)\\d+\\?$/, 'gm'); const input = `%B6545461234613451^DOE/JOHN^00000000000000000000000?;6545461234613451=984651465116111?`; var match = regex.exec(input); document.write(match.length);

Answer 2

It seems that it has something to do with escape character. I have tried on Chrome Developer tools running the following two lines.

1. Without Template Literal
new RegExp("^\%B(\d+)\^(\w+)\/(\w+)\^\d+\?;\d+=(\d\d)(\d\d)\d+$").exec('%B6545461234613451^DOE/JOHN^00000000000000000000000?;6545461234613451=984651465116111?')

result: null

2. With Template Literal
new RegExp($`{"^\%B(\d+)\^(\w+)\/(\w+)\^\d+\?;\d+=(\d\d)(\d\d)\d+$"}`).exec('%B6545461234613451^DOE/JOHN^00000000000000000000000?;6545461234613451=984651465116111?')

result: ["O", index: 20, input: "%B6545461234613451^DOE/JOHN^00000000000000000000000?;6545461234613451=984651465116111?", groups: undefined]

Wrapping your Regex expression in a Template Literal should solve the problem. The compile process has likely took the wild card characters into account during the build, which suggests why it works after compilation.