JSFiddle - React, Tailwind, and code Playground

JavaScript

var Str2 = function(strs, str){    
    var i, a = 0;	
    for(i=0; i < strs.length; i++){        
        if (str == strs[i] ) {
            a = a + 1;                       
        }
        if (a > 1) {
            return "true";
        } 
    }
    return 'false';
}

alert(Str2(["a", "b", "a", "c"], "a"));