JSFiddle - React, Tailwind, and code Playground

JavaScript

function scopedEval(str, scope) {
   var toCheck = str.split(' || ');
    for(var i = 0; i < toCheck.length; ++i){
        if(scope[toCheck[i]])
            return scope[toCheck[i]];
    }
}

var scope = { first:1, second:2 };

var expr1  = "second || first";
var expr2  = "third || second || first";

alert( scopedEval(expr1,scope) );
alert( scopedEval(expr2,scope) );