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JavaScript

Posted by Alexander D
Alexander D
8,685 Points

Looping through an Array of objects

Hello there,

I am trying loop through an array of object. My code works fine but can be optimized:

var students = [

  {name: "Jack", track: "iOS", achievement: 5},
  {name: "Alex", track: "Javascript", achievement: 7},
  {name: "Robert", track: "Python", achievement: 0},
  {name: "Jill", track: "Ruby", achievement: 15},
 {name: "Angus", track: "C++", achievement: 3}
]

var input = prompt ("Give me a name, track or Achievement")

for (var i = 0; i < students.length; i++) { 

if ( input === students[i].name || input === students[i].track || input === students[i].achievement) { 

alert(input)
} 
  }

The scope of this code is to return data if there's a match in the system or database. As you can see in my IF statement I am declaring 3 arguments. What If my object has 200 properties like "address", "score", "color", etc.? It doesn't seem logical to me to declare all of them in an IF statement.

What I am trying to do is something like:

if ( input matches any of the properties of the object) {

alert(object property)

}

Thanks!

4 Answers

KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,967 Points

I guess it depends on what you are logging. If you log student just after student = students[i] inside the loop you should see an entry in the console for each student. If you log student after the loops you should see one entry - the last student. Maybe I don't understand what you are saying.

student is a variable for the individual objects in students. So for the first iteration student is:

{name: "Jack", track: "iOS", achievement: 5}

Then there is a second loop for each key of the current student:

for (var k in student)

k is the key (in this case name, track, achievement)

student[k] is the value for that key ("Jack", "iOS", 5)

A comparison is made between the value and input and if there is a match an alert is displayed.

The code then continues with the next student.

Note: I'd like to change my input comparison to use == instead of ===. 

if (student[k] == input)

Currently with the type being checked, inputting one of the numeric values does not result in an alert because input is a string.

KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,967 Points
KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,967 Points

There are probably other (better?) ways to do this but this is what I came up with:

var students = [

  {name: "Jack", track: "iOS", achievement: 5},
  {name: "Alex", track: "Javascript", achievement: 7},
  {name: "Robert", track: "Python", achievement: 0},
  {name: "Jill", track: "Ruby", achievement: 15},
 {name: "Angus", track: "C++", achievement: 3}
]

var input = prompt ("Give me a name, track or Achievement")

for (var i = 0; i < students.length; i++) { 
  student = students[i]

  for (var k in student) {
      if (student[k] === input) {
          alert(input)
      } 
  }
}
Alexander D
Alexander D
8,685 Points
Alexander D
Alexander D
8,685 Points

Hello KRIS NIKOLAISEN ,

Thanks for your response! Coul you walk me through your solution if you have time?

Your code seems to be working. I am not sure about the following statement. I am breaking this a bit:

var students = [

  {name: "Jack", track: "iOS", achievement: 5},
  {name: "Alex", track: "Javascript", achievement: 7},
  {name: "Robert", track: "Python", achievement: 0},
  {name: "Jill", track: "Ruby", achievement: 15},
 {name: "Angus", track: "C++", achievement: 3}
]

for (var i = 0; i < students.length; i++) { 
  student = students[i]

}

If I consol.log the result, I am getting {name: "Angus", track: "C++", achievement: 3}, which is the last object. It seems that your loop is creating a new object "student" that includes the last result of the loop.

The second part of your nested loop starts like this:

for (var k in student) { if (student[k] === input)

My student "student" is Angus. Even when I input Alex I get the last result "Angus". How can student[k] === input?

Thanks for your time!

Alexander D
Alexander D
8,685 Points
Alexander D
Alexander D
8,685 Points

KRIS NIKOLAISEN Thanks for the explanation!

I am not sure, but it seems I was logging the incorrect data.

If I console.log(student) after the first loop I am able to see all the students, tracks and achievements. I am not sure why it was logging only the last student.

Thanks again!