Can someone please clarify why the countOnlineUsers variable does not retain its value in memory when console logging?

Question

Can someone please clarify why the countOnlineUsers variable does not retain its value in memory when console logging?

I'm attempting to iterate through a bi-dimensional object to count the number of users whose online status is set to true. However, when I try to log the countOnlineUsers variable using console.log(), the count doesn't persist and appears to reset each time the loop encounters a "new" user with an "online" property.

    let users = {
      Alan: {
        age: 27,
        online: false
      },
      Jeff: {
        age: 32,
        online: true
      },
      Sarah: {
        age: 48,
        online: false
      },
      Ryan: {
        age: 19,
        online: true
      },
      George: {
        age: 32,
        online: true
      }
    };
    
    function countOnline(obj) {
    
      for(let user in users) {

    if (!users.hasOwnProperty(user)) continue; // Initial check

      let obj = users[user];     
      for(let prop in obj) {
        if (!obj.hasOwnProperty(prop)) continue; // Secondary check

          let countOnlineUsers = 0;
          if(obj[prop] === true) {            
            countOnlineUsers++;
          }
          console.log(prop + " = " + obj[prop]);
          console.log(countOnlineUsers);        
      }        
  

    }

    }
    
    console.log(countOnline(users));

javascript object iteration

Answer 1

Answer №1

On each loop iteration, you are consistently assigning the value of 0:

for(let user in users) {
    //...
    let countOnlineUsers = 0;
    //...
}

As you only change the value once within that iteration, it will always be either 0 or 1. To resolve this, initialize the value before the loop:

let countOnlineUsers = 0;
for(let user in users) {
    //...
}

This way, every loop iteration will adjust the same value (if the condition is met), instead of creating a new one each time.

(Please note there are nested loops, thus I made an educated guess on which one needed to increment the value.)

Your modified original code:

let users = {
      Alan: {
        age: 27,
        online: false
      },
      Jeff: {
        age: 32,
        online: true
      },
      Sarah: {
        age: 48,
        online: false
      },
      Ryan: {
        age: 19,
        online: true
      },
      George: {
        age: 32,
        online: true
      }
    };
    
    function countOnline(obj) {
    
      let countOnlineUsers = 0;
      for(let user in users) {

    if (!users.hasOwnProperty(user)) continue; //Initial check

      let obj = users[user];     
      for(let prop in obj) {
        if (!obj.hasOwnProperty(prop)) continue; //Secondary check

          if(obj[prop] === true) {            
            countOnlineUsers++;
          }
          console.log(prop + " = " + obj[prop]);
          console.log(countOnlineUsers);        
      }        
  

    }

    }
    
    console.log(countOnline(users));

Answer 2

On each loop iteration, you are consistently assigning the value of 0:

for(let user in users) {
    //...
    let countOnlineUsers = 0;
    //...
}

As you only change the value once within that iteration, it will always be either 0 or 1. To resolve this, initialize the value before the loop:

let countOnlineUsers = 0;
for(let user in users) {
    //...
}

This way, every loop iteration will adjust the same value (if the condition is met), instead of creating a new one each time.

(Please note there are nested loops, thus I made an educated guess on which one needed to increment the value.)

Your modified original code:

let users = {
      Alan: {
        age: 27,
        online: false
      },
      Jeff: {
        age: 32,
        online: true
      },
      Sarah: {
        age: 48,
        online: false
      },
      Ryan: {
        age: 19,
        online: true
      },
      George: {
        age: 32,
        online: true
      }
    };
    
    function countOnline(obj) {
    
      let countOnlineUsers = 0;
      for(let user in users) {

    if (!users.hasOwnProperty(user)) continue; //Initial check

      let obj = users[user];     
      for(let prop in obj) {
        if (!obj.hasOwnProperty(prop)) continue; //Secondary check

          if(obj[prop] === true) {            
            countOnlineUsers++;
          }
          console.log(prop + " = " + obj[prop]);
          console.log(countOnlineUsers);        
      }        
  

    }

    }
    
    console.log(countOnline(users));

Answer 3

Answer №2

The reason for this issue is that the variable countOnlineUsers is defined inside the loop. It should be declared outside of it and then updated within the loop.

let users = {
      Alan: {
        age: 27,
        online: false
      },
      Jeff: {
        age: 32,
        online: true
      },
      Sarah: {
        age: 48,
        online: false
      },
      Ryan: {
        age: 19,
        online: true
      },
      George: {
        age: 32,
        online: true
      }
    };
    
    function countOnline(obj) {
      let countOnlineUsers = 0;
      for(let user in users) {

    if (!users.hasOwnProperty(user)) continue; //First check

      let obj = users[user];     
      
      for(let prop in obj) {
        if (!obj.hasOwnProperty(prop)) continue; //Second check

          
          if(obj[prop] === true) {            
            countOnlineUsers++;
          }
          console.log(prop + " = " + obj[prop]);
          console.log(countOnlineUsers);        
      }        
  

    }

    }
    
    console.log(countOnline(users));

Answer 4

The reason for this issue is that the variable countOnlineUsers is defined inside the loop. It should be declared outside of it and then updated within the loop.

let users = {
      Alan: {
        age: 27,
        online: false
      },
      Jeff: {
        age: 32,
        online: true
      },
      Sarah: {
        age: 48,
        online: false
      },
      Ryan: {
        age: 19,
        online: true
      },
      George: {
        age: 32,
        online: true
      }
    };
    
    function countOnline(obj) {
      let countOnlineUsers = 0;
      for(let user in users) {

    if (!users.hasOwnProperty(user)) continue; //First check

      let obj = users[user];     
      
      for(let prop in obj) {
        if (!obj.hasOwnProperty(prop)) continue; //Second check

          
          if(obj[prop] === true) {            
            countOnlineUsers++;
          }
          console.log(prop + " = " + obj[prop]);
          console.log(countOnlineUsers);        
      }        
  

    }

    }
    
    console.log(countOnline(users));

Can someone please clarify why the countOnlineUsers variable does not retain its value in memory when console logging?

Answer №1

Answer №2

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