I'm trying to make an id searcher which does a thing when you input the right id. However, the JavaScript if statement always runs. How?

In JavaScript, using the assignment operator (=) instead of comparison operators (== or ===) in an if statement causes the condition to always evaluate as true. This is because assignment returns the assigned value, which is typically truthy.

The Problem: Assignment vs Comparison

When you accidentally use = in a condition, you're assigning a value instead of comparing:

let searchId = 10001;
let currentId = 10002;

// Wrong: This assigns searchId to currentId and always runs
if (currentId = searchId) {
    console.log("This always runs! currentId is now:", currentId);
}

// Right: This compares the values
if (currentId === searchId) {
    console.log("This only runs when they match");
}

This always runs! currentId is now: 10001

Correct ID Search Implementation

Here's how to properly implement an ID searcher using the strict equality operator (===):

var details = [
    {
        id: 10001,
        name: "John"
    },
    {
        id: 10002,
        name: "Bob"
    },
    {
        id: 10003,
        name: "Carol"
    },
    {
        id: 10004,
        name: "David"
    }
];

var searchId = 10003;
var found = false;

for (var index = 0; index < details.length; index++) {
    if (details[index].id === searchId) {
        console.log("ID " + details[index].id + " found: " + details[index].name);
        found = true;
        break;
    }
}

if (!found) {
    console.log("ID " + searchId + " not found");
}

ID 10003 found: Carol

Comparison of Operators

Modern Approach Using Array Methods

For a more elegant solution, consider using Array.find():

var details = [
    { id: 10001, name: "John" },
    { id: 10002, name: "Bob" },
    { id: 10003, name: "Carol" },
    { id: 10004, name: "David" }
];

var searchId = 10003;
var result = details.find(function(item) {
    return item.id === searchId;
});

if (result) {
    console.log("Found:", result.name);
} else {
    console.log("ID not found");
}

Found: Carol

Conclusion

Always use comparison operators (== or ===) in if statements, never assignment (=). The strict equality operator (===) is recommended as it prevents unexpected type coercion issues.