javascript regular expression to not match a word

94
votes

How do I use a javascript regular expression to check a string that does not match certain words?

For example, I want a function that, when passed a string that contains either abc or def, returns false.

'abcd' -> false

'cdef' -> false

'bcd' -> true

EDIT

Preferably, I want a regular expression as simple as something like, [^abc], but it does not deliver the result expected as I need consecutive letters.

eg. I want myregex

if ( myregex.test('bcd') ) alert('the string does not contain abc or def');

The statement myregex.test('bcd') is evaluated to true.

6
javascriptregexstring

6 Answers

142
votes

This is what you are looking for:

^((?!(abc|def)).)*$

The ?! part is called a negative lookahead assertion. It means "not followed by".

The explanation is here: Regular expression to match a line that doesn't contain a word

20
votes
if (!s.match(/abc|def/g)) {
    alert("match");
}
else {
    alert("no match");
}
5
votes

Here's a clean solution:

function test(str){
    //Note: should be /(abc)|(def)/i if you want it case insensitive
    var pattern = /(abc)|(def)/;
    return !str.match(pattern);
}
1
votes
function test(string) {
    return ! string.match(/abc|def/);
}
0
votes
function doesNotContainAbcOrDef(x) {
    return (x.match('abc') || x.match('def')) === null;
}
0
votes

This can be done in 2 ways:

if (str.match(/abc|def/)) {
                       ...
                    }


if (/abc|def/.test(str)) {
                        ....
                    }