How to identify and correct the logical error?

Question

Can someone help me finding the logical error in the code bellow? When it runs, the program displays all as "not guilty" despite one of the objects in the array satisfies the condition.

var suspectsArray = [
{ 
    "name": "BRIDGET ASHELY",
    "glasses": "very thick",
    "accessory": "metal briefcase",
    "eyes": "pale",
    "height": 155,
    "age": 63
},
{ 
    "name": "LIANNE NIEMELA",
    "glasses": "blue",
    "accessory": "plastic box",
    "eyes": "brown",
    "height": 150,
    "age": 47
},
{ 
    "name": "JAUNITA FORSLIN",
    "glasses": "dark brown",
    "accessory": "laptop bag",
    "eyes": "grey",
    "height": 182,
    "age": 58
},
{ 
    "name": "JULIANA DEAUVILLE",
    "glasses": "red",
    "accessory": "glass bottle",
    "eyes": "green",
    "height": 175,
    "age": 34
},
{ 
    "name": "LINETTE DORCEY",
    "glasses": "light tan",
    "accessory": "big black envelope",
    "eyes": "blue",
    "height": 178,
    "age": 43
}
];

var myFont;
var backgroundImg;

function preload() {
 myFont = loadFont('SpecialElite.ttf');
 backgroundImg = loadImage("Background.png");
}

function setup()
{
createCanvas(640,480);
textFont(myFont);
}


function matchSuspect(suspectObj){

    for (var k = 0; k < suspectsArray.length; k++)
    {
        if(
        suspectsArray[k].glasses == "blue" &&
        suspectsArray[k].accessory == "plastic box" &&
        suspectsArray[k].eyes == "brown" &&
        suspectsArray[k].height > 141 &&
        suspectsArray[k].age < 49
    ){
        return true;
    }

        return false;
    }
    }
function draw()
{

  image(backgroundImg, 0, 0);

  for(let i = 0 ; i < suspectsArray.length; i++){
    if(matchSuspect(suspectsArray[i]) == true){
      fill(255,0,0);
      text(suspectsArray[i].name + " is guilty!", 60, 60 + i * 20);
    }else{
      fill(0,155,0);
      text(suspectsArray[i].name + " is not guilty", 60, 60 + i * 20 );
    }
  }
}

If running correctly, it should display the second object in the array in red. I am not sure if the iterations are wrong or what. To experiment with that I tried using || instead of && and the logic was correct (or so the program gave the right answers).

It looks to me like a simple solution, but I spend a very long time on it and couldn't get to it :/

Answer 1

The issue here is that your function ignores the object passed in as a parameter and instead loops through the entire array, but will return as soon as the first person is checked, hence why you are always getting false for every person passed in as a parameter.

To fix this, try removing your for loop inside the function and only process the object being passed in as the parameter instead.

function matchSuspect(suspectObj){

    if(
    suspectObj.glasses == "blue" &&
    suspectObj.accessory == "plastic box" &&
    suspectObj.eyes == "brown" &&
    suspectObj.height > 141 &&
    suspectObj.age < 49
    ){
      return true;
    }

    return false;
}

Answer 2

• matchSuspect - pass suspects and suspect to it, for better code quality.
• draw - pass suspects and matchSuspect to it
• use === not ==
• fix your styling, would be easier to see.
• you loop twice, once in matchSuspect and once in draw, remove the loop from one of them.

You need an else after your true, you return false after the first element in your array.

Answer 3

matchSuspect() should only test the one subject that's passed in suspectObj.

function matchSuspect(suspectObj) {
  return suspectObj.glasses == "blue" &&
    suspectObj.accessory == "plastic box" &&
    suspectObj.eyes == "brown" &&
    suspectObj.height > 141 &&
    suspectObj.age < 49;
}

Answer 4

In the matchSuspect function, when the first iteration runs for the first object of the array, the condition in the if is false and so it gets to the return false; expression and the entire function ends and you don't get to do the other iterations. Basically this means that the function always returns false.

Furthermore, you don't really use the matchSuspect function's parameter suspectObj. Did you mean to do something else?

Maybe you wanted to do something like this?

function matchSuspect(suspectObj) {
    if (suspectObj.glasses == "blue" &&
        suspectObj.accessory == "plastic box" &&
        suspectObj.eyes == "brown" &&
        suspectObj.height > 141 &&
        suspectObj.age < 49
    ) {
        return true;
    }
    
    return false;
}

function draw() {
    image(backgroundImg, 0, 0);

    for(let i = 0 ; i < suspectsArray.length; i++) {
        if (matchSuspect(suspectsArray[i]) == true) {
            fill(255,0,0);
            text(suspectsArray[i].name + " is guilty!", 60, 60 + i * 20);
        } else {
            fill(0,155,0);
            text(suspectsArray[i].name + " is not guilty", 60, 60 + i * 20 );
        }
    }
}