在javascript中为函数设置参数typeof

Question

i would like my code to return 'invalid age' if the parameter given in the function is not a number,instead am getting a system referenceError.any one who can help out?

function canIWatch(age){
   this.age = age
  if ( age >=1 && age <= 6 ) {
    return "You are not allowed to watch Deadpool after 6.00pm.";
}
else if (age >= 7 && age <= 17){
    return "You must be accompanied by a guardian who is 21 or older.";
}
else if (age >= 18 && age <= 24){
    return "You are allowed to watch Deadpool, right after you show some ID.";
}
else if (age >= 25 ){
    return "Yay! You can watch Deadpool with no strings attached!";
}
else if (typeof age !== 'number'){
  return "Invalid age.";
  }
} 

the code below is to pass the tests below. edited code;

function canIWatch(age){
   this.age = age
if (typeof age !== 'number' || age <=0){
      return "Invalid age.";
}
else if ( age >=1 && age <= 6 ) {
    return "You are not allowed to watch Deadpool after 6.00pm.";
}
else if (age >= 7 && age <= 17){
    return "You must be accompanied by a guardian who is 21 or older.";
}
else if (age >= 18 && age <= 24){
    return "You are allowed to watch Deadpool, right after you show some    ID.";
}
else if (age >= 25 ){
    return "Yay! You can watch Deadpool with no strings attached!";
}
}

test codes for the function;

describe('canIWatch tests', function () {
  it('Should return the appropriate message for age less than 6', function () {
expect(canIWatch(5)).toEqual('You are not allowed to watch Deadpool after 6.00pm.');});

  it('Should return the appropriate message for age less than 17', function () {
expect(canIWatch(15)).toEqual('You must be accompanied by a guardian who is 21 or older.');  });

  it('Should return the appropriate message for age less than 25', function () {
expect(canIWatch(20)).toEqual('You are allowed to watch Deadpool, right after you show some ID.'); });

  it('Should return the appropriate message for age above 25 than 6', function () {
expect(canIWatch(30)).toEqual('Yay! You can watch Deadpool with no strings attached!');});

  it('should return an appropriate message if provided age is invalid', function () {
expect(canIWatch(-1)).toEqual('Invalid age.');});});

the question is;

Deadpool is an R-rated movie. Write a JavaScript function named canIWatch that will take age as a parameter. If the age is less than 6, return You are not allowed to watch Deadpool after 6.00pm. If the age is 6 or more but less than 17, return You must be accompanied by a guardian who is 21 or older. If the age is 17 or more but less than 25, return You are allowed to watch Deadpool, right after you show some ID. If the age is 25 or greater, return Yay! You can watch Deadpool with no strings attached!. If the age is invalid, return Invalid age.

Answer 1

Here you go. Your code didn't work because the function automatically parses the string into an integer. Just try by yourself by typing in the console: '123' > 23 or false < 32 .

Using mathematical operators will always parse it's components into integers. That's why the validation have to be on the first position.

 age = '12'; if (typeof age !== 'number') { console.log("Invalid age."); } else if (age >= 1 && age <= 6) { console.log("You are not allowed to watch Deadpool after 6.00pm."); } else if (age >= 7 && age <= 17) { console.log("You must be accompanied by a guardian who is 21 or older."); } else if (age >= 18 && age <= 24) { console.log("You are allowed to watch Deadpool, right after you show some ID."); } else if (age >= 25) { console.log("Yay! You can watch Deadpool with no strings attached!"); }

Answer 2

If the value passed in isn't a number then it's definitely not going to >= 1 or whatever so there's really no need at the point testing it. If you move your test for your typeof number up the top your function I'm tipping it will probably solve your problem:

function canIWatch(age){
  if (typeof age !== 'number') return "Invalid age.";

  this.age = age
  if ( age >=1 && age <= 6 ) {
    return "You are not allowed to watch Deadpool after 6.00pm.";
  }
  else if (age >= 7 && age <= 17){
    return "You must be accompanied by a guardian who is 21 or older.";
  }
  else if (age >= 18 && age <= 24){
    return "You are allowed to watch Deadpool, right after you show some ID.";
  }
  else if (age >= 25 ){
    return "Yay! You can watch Deadpool with no strings attached!";
  }
} 

Answer 3

 function canIWatch(age) { if (age >= 1 && age <= 6) { return "You are not allowed to watch Deadpool after 6.00pm."; } else if (age >= 7 && age <= 17) { return "You must be accompanied by a guardian who is 21 or older."; } else if (age >= 18 && age <= 24) { return "You are allowed to watch Deadpool, right after you show some ID."; } else if (age >= 25) { return "Yay! You can watch Deadpool with no strings attached!"; } else if (isNaN(age)) { return "Invalid age."; } else if (!age) { return "Age must be informed."; } } function checkMyAge() { var age = document.querySelector('#ageInput').value; alert(canIWatch(age)); }

 <input id="ageInput" type="text" /> <button onclick="checkMyAge()">Check</button>