jQuery: Check if character is in string

var str = "i am a string with _";
if (str.indexOf('_') == -1) {
   // will not be triggered because str has _..
}

and as spender said below on comment, jQuery is not a requirement.. indexOf is a native javascript

There are several ways to do this.

1. indexOf() method:

   if( str.indexOf('_') != -1 ){
      //do something
   }
   else{
      //do something 
   } 
   

2. Search() method:

    if( str.search("_")!=-1 ){
      //do something
    } 
    else {
     //Do something 
    }
   

3. :contains() selector:

    if( $("p:contains(_)") ).length{
      //Do something
    }
    else{
      //Do something
    }
   

4. using a regular expression:

    if( str.match(/_/g) ).length{
      //Do something
    }
    else{
      //Do something
    }
   

I think the first method is the simplest way.