Help with wikipeida Viewer!

Hello. please help me tell me where is the error
the for loop doesn’t work for me

I don’t know where is the problem??

the console tell me the “repons[1].length” is not defined

yes the success function is work correctly

console.log(repons); it work for me !!! it get the success repons

this is my for loop but doesn’t work !!

for(var i = 0; i < repons[1].length; i++) {
    $("#output").append("<div class='well'><a href="+repons[3][i]+"><h2>" + repons[1][i]+ "</h2>" + "<p>" + repons[2][i] + "</p></a></div>");
    
  }