为什么我的 javascript 代码没有显示“未找到”？

Question

it doesnt show Not Found , it shows undefined

 function checkObj(obj, checkprob) { if (obj.hasOwnProperty) { return obj[checkprob]; } else { return "Not Found" } } console.log(checkObj({ gift: "pony", pet: "kitten", bed: "sleigh" }, "Amir"))

Answer 1

You are using hasOwnProperty wrong:

 function checkObj(obj, checkprob){ if(obj.hasOwnProperty(checkprob)){ return obj[checkprob]; } else{ return "Not Found"; } } console.log(checkObj({gift: "pony", pet: "kitten", bed: "sleigh"}, "Amir")); console.log(checkObj({gift: "pony", pet: "kitten", bed: "sleigh"}, "bed"));

Answer 2

hasOwnProperty is a method and it takes a parameter. You have to call it like this hasOwnProperty(checkprob) . See also the documentation .

 function checkObj(obj, checkprob) { if (obj.hasOwnProperty(checkprob)) { return obj[checkprob]; } else { return "Not Found" } } console.log(checkObj({ gift: "pony", pet: "kitten", bed: "sleigh" }, "Amir"))

Answer 3

Missing function call. You can also use in operator.

function checkObj(obj, checkprob){
     if(obj.hasOwnProperty(checkprob)){
          return obj[checkprob];
     } else{
          return "Not Found";
     } 
}


    function checkObj2(obj, checkprob) {
      if (checkprob in obj) {
        return obj[checkprob];
      } else {
        return "Not Found";
      }
    }

    console.log(
      checkObj2(
        {
          gift: "pony",
          pet: "kitten",
          bed: "sleigh"
        },
        "Amir"
      )
    );