Using regular expression ,if and else conflict with .test() function.

Question

Hi In the given code, best.test(password) is returning true but when I am using it in if() condition in takes it as a false.

Code:

if(best.test(password))              //It takes it as a false .
{
    document.write(best.test(password));
    tdPwdStrength.innerHTML="best"+best.test(password);  //but in actual it is true and returning true. 
}

Please Suggest!

Answer 1

What is best? Is it a ‘global’ RegExp, that is, one with the g flag set?

If so, then each time you call test or exec you will get a different answer, as it remembers the previous string index and searches from there:

var r= /a/g;                // or new RegExp('a', 'g')
alert(r.test('aardvark'));  // true. matches first `a`
alert(r.test('aardvark'));  // true. matches second `a`
alert(r.test('aardvark'));  // true. matches third `a`
alert(r.test('aardvark'));  // false! no more matches found
alert(r.test('aardvark'));  // true. back to the first `a` again

JavaScript's RegExp interface is full of confusing little traps like this. Be careful.