将特定的正则表达式模式与我的字符串匹配

Question

Hi I would like my regex pattern to match a character with a pattern of 0-9 and multiply and add operator. So far this is what I have done.

var regexPattern = /\d\+\*/;

function matchPattern( regexPattern, mycharacter ) {
    if ( mycharacter.match( regexPattern ) ) {
        console.log( 'true' );
    } else {
        console.log( 'false' );
    }
}

matchPattern( regexPattern, '+' );

the problem is when I pass the pattern like a number or a '+' or '*' sign it returns false instead. What am I doing wrong?

Answer 1

Change this line:

var regexPattern = [/\d\+\*/];

To this:

var regexPattern = /[\d\+\*]/;

Or, noting that you don't need to escape + or * when used within [] :

var regexPattern = /[\d+*]/;

You were creating an array containing a single element that is a regex. What you want is a regex that uses the [] as part of its pattern.

The pattern [\\d+*] will match a digit ( \\d ) or a plus sign ( + ) or an asterisk ( * ).

UPDATE for your edit: the pattern /\\d\\+\\*/ that you have will match a digit that is followed immediately by a plus sign that is followed by an asterisk. See above for the pattern you need.

Answer 2

You need to put the square brackets inside the regex: /[\\d\\+\\*]/ this means that it will match any of the characters in the square brackets.

To match more than just one character, you'll need to put a + or * on the end: /[\\d\\+\\*]+/ to tell it to keep matching any number of digits, asterisks and plus signs.