javascript - How to pass a regular expression as a function parameter

Question

Why this returns false instead of true.

function doit(expression) {

    var regex = new RegExp(expression, 'g');

    alert(regex.test('[email protected]'));
}

doit("/^w+([-+.']w+)*@w+([-.]w+)*.w+([-.]w+)*/");
?

http://jsfiddle.net/hAV8Q/

Answer 1

Either format your expression properly:

function doit(expression) {
    var regex = new RegExp(expression, 'g');
    alert(regex.test('[email protected]'));
}

doit("^\w+([-+.\']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*");
// no / here, escape 

or pass the expression directly:

function doit(expression) {
    alert(expression.test('[email protected]'));
}

doit(/^w+([-+.']w+)*@w+([-.]w+)*.w+([-.]w+)*/g);

?

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The slashes (/) are not part of the expression, they denote a regex literal. If you use a string containing the expression, you have to omit them and escape every backslash since the backslash is the escape character in strings as well.