RegEx to find sequence within a string with optional start and end points-CodePudding

I have a string that can optionally contain "ob_" in the beginning and optionally "~..." in the end, examples:

ob_name
name
ob_name~213334dsf34n
name~kjdsf8943j

In each case, I want to get name returned. However, I don't get the RegEx to work. I tried using /^(ob_)?(. )(~. )?$/ of which I thought it reads like "ob_ in the beginning contained zero or one times, string sequence in the midde, ~ plus random chars in the end".

What do I do wrong?

CodePudding user response：

If you don't need to catch the ob_ or ~xxx, you can try:

$s = 'ob_name~213334dsf34n';
if (preg_match('/^(?:ob_)?(. ?)(?:~. )?$/',$s,$matches)) {
    var_dump($matches[1]); // this is the name you want
}

CodePudding user response：

Match returns an array, where each index is represented by the ()'s in your regexp.

/^(ob_)?(. ?)(~. )?$/i

    (ob_) = index 0
    (. ?) = index 1
    (~. ) = index 2

So to get the value, you'd do a match on the string, which returns an array,

var myStr = "ob_name~213334dsf34n";
var match = myStr.match(/^(ob_)?(. ?)(~. )?$/i);

... then you'd grab index "2":

var result = match[2]; // "name"

... be careful, this regexp can return match when ob_ and ~ not present, so some extra processing will be needed:

var myStr = "ob_name~213334dsf34n";
var match = myStr.match(/^(ob_)?(. ?)(~. )?$/i);
// match[0] = "ob_name~213334dsf34n"
// match[1] = "ob_"
// match[2] = "name"
// match[3] = "~213334dsf34n"
var result;
if(match){
    if( (match[0] && match[0].indexOf("ob_")) > -1 || (match[3] && match[3].indexOf("~") > -1 ){
        result = match[2];
    }
}
console.log(result || "not found")

test cases:

var cases = [
    "ob_name",
    "name",
    "ob_name~213334dsf34n",
    "name~kjdsf8943j",
    "bob",
    "sally"
];

for(var i=0; i<cases.length; i  ){
    var match = cases[i].match(/^(ob_)?(. ?)(~. )?$/i);
    var result = null;
    if(match){
        if( (match[0] && match[0].indexOf("ob_")) > -1 || (match[3] && match[3].indexOf("~")) > -1 ){
            result = match[2];
        }
    }
    //console.log(match)
    console.log(result || "not found")
}

CodePudding user response：

I think you're all overthinking this.

(ob_)?([^~] )

Using preg_match, the desired match will be stored in [2].

Foul