Javascript check if string if true or false and convert to Boolean

Question

Is there a better way to improve the below statement to check if the val() is 'true' or 'false' and if it is then it will change it to a Boolean. The reason being, some of the values may be a word.

var thisval = $(this).val();
if (thisval == "true"){
    ao[id] = true;
} else if (thisval == "false"){
    ao[id] = false;
} else {
    ao[id] = $(this).val();
}

Answer 1

String.prototype.bool = function() {
    return (/^true$/i).test(this);
};


if ( $(this).val() == "true" ||  $(this).val() == "false") {
    ao[id] = $(this).val().bool();
}else {
    ao[id] = $(this).val();
}

Answer 2

Most readable:

var thisval = $(this).val();
ao[id] = thisval === 'true' ? true : 
         thisval === 'false' ? false : 
         thisval;

One-liner based on the conditional operator:

var thisval = $(this).val();
ao[id] = thisval === 'true' ? true : (thisval === 'false' ? false : thisval);

One-liner based on || and && behavior:

var thisval = $(this).val();
ao[id] = thisval === 'true' || (thisval !== 'false') && thisval || false;

Shortest one-liner (combination of the above):

var thisval = $(this).val();
ao[id] = thisval === 'true' || (thisval === 'false' ? false : thisval);

Answer 3

Try JSON.parse().

"true" and "false" are actually json representations of true, false. This is how ajax parses json object as a string from server side. If on server side, we return true, false => the browser will receive it as a string "true" or "false" (json representation)

if ( $(this).val() == "true" ||  $(this).val() == "false") {
    ao[id] = JSON.parse($(this).val());
}else {
    ao[id] = $(this).val();
}

DEMO