You can find the largest among three numbers using the if...else statement.

Example 1: Largest Number Among Three Numbers

// program to find the largest among three numbers

// take input from the user
let num1 = parseFloat(prompt("Enter first number: "));
let num2 = parseFloat(prompt("Enter second number: "));
let num3 = parseFloat(prompt("Enter third number: "));
let largest;

// check the condition
if(num1 >= num2 && num1 >= num3) {
    largest = num1;
}
else if (num2 >= num1 && num2 >= num3) {
    largest = num2;
}
else {
    largest = num3;
}

// display the result
console.log("The largest number is " + largest);

Output

Enter first number: -7
Enter second number: -5
Enter third number: -1
The largest number is -1

In the above program, parseFloat() is used to convert numeric string to number. If the string is a floating number, parseFloat() converts the string into floating point number.

The numbers are compared with one another using greater than or equal to >= operator. And the if...else if...else statement is used to check the condition.

Here, logical AND && is also used to check two conditions.

You can also use the JavaScript built-in Math.max() function to find the largest among the numbers.

Example2: Using Math.max()

// program to find the largest among three numbers

// take input from the user
let num1 = parseFloat(prompt("Enter first number: "));
let num2 = parseFloat(prompt("Enter second number: "));
let num3 = parseFloat(prompt("Enter third number: "));

let largest = Math.max(num1, num2, num3);

// display the result
console.log("The largest number is " + largest);

Output

Enter first number: 5
Enter second number: 5.5
Enter third number: 5.6
The largest number is 5.6

Math.max() returns the largest number among the provided numbers.

You can use Math.min() function to find the smallest among the numbers.