Why doesnt this Javascript regular expression work

Question

var existing = "";   
if(disk.isLinux){   
    var valinvalid = "/usr" ;            
    var valinput = /^\/[a-zA-Z]{2,}/ ;  
    if(!valinput.match(valinvalid)){      
        return "^/" + existing + "[^/][a-zA-Z]{2,}[^/]$";
    } 
}

Here im trying to do the following in the first if condition ie. if(disk.isLinux):
1. there should be minimum 3 characters
2. the first character should be /
3. the entire input shouldnt match "/usr". But it can be /us or /usra

Could you postr some examples of what should match and what shouldn't? — nana
– nana, Commented Feb 28, 2012 at 14:47
Other than the default linux directories like /usr, /root etc... anything else with minimum 3 characters and starting with / is a valid input — Pradeep
– Pradeep, Commented Feb 28, 2012 at 14:50
Try running it on regular-expressions.info/javascriptexample.html. It worked for me on Firefox and Chrome — Santosh Gokak
– Santosh Gokak, Commented Feb 28, 2012 at 14:57

nana · Accepted Answer · 2012-02-28 14:56:34Z

1

If you are just trying to test if it matches, us test on regexp:

/^\/[\w]{2,}/.test("/usr/");     //true

Is this what you are trying to do?

answered Feb 28, 2012 at 14:56

nana

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1 Comment

Pradeep Over a year ago

Thank you guys for your support return "^/" + existing + "(?!usr$)[a-zA-Z]{0,}$";- This worked.

Roderick Obrist · Accepted Answer · 2012-02-28 14:53:58Z

0

A couple of things:

1) vars should never ever ever be inside if statements

2) String.prototype.match exists RegExp.prototype.match does not

But more importantly, you dont need regEx at all

if (
 input.length < 3 ||
 input.charAt(0) !== '/' ||
 input === '/user'
) {
 throw new Error("I'm not happy with the input");
}

answered Feb 28, 2012 at 14:53

Roderick Obrist

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Comments

Vikram · Accepted Answer · 2012-02-28 15:00:53Z

0

try changing your code to use:

var valinput = new RegExp("/^\/[a-zA-Z]{2,}/") ;  
 if(!valinput.test(valinvalid)){

answered Feb 28, 2012 at 15:00

Vikram

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