Need help finding max value in java script (without max method)

Variables declared with the let keyword have a block scope, that is, they are only accessible within the block they were defined in. You are first setting max to a, then inside your if statement, you are creating another local variable with the same name and assigning it the value b. What you should do is remove the let declarations inside your if/else statement.

Second, your if block is being exited when the first condition is satisfied. You should use another if statement (which will run regardless of whether or not the condition in the first one is met) as opposed to an else statement (which will only run if the first condition is not met).

Third, you are passing an object reference to your function in your console.log (all functions are objects in javascript) which is equivalent to the function text. You need to pass the function call instead.

That's all you need to do, besides not using undefined variables.

const number1 = 54;
const number2 = 72;
const number3 = 189;

const getMax = (a, b, c) => {
  let max = a;
  
  if(b > max) {
    max = b;
  }
  
  if (c > max){
    max = c;
  };
  
  return max;
}

console.log(`Nilai maksimum adalah ${getMax(number1, number2, number3)}`);

I see many errors. First, you initialize max 2 times. let max = a; and then you can use max. But the else if is also wrong.

What if c < b < a? Then only the first if applies although c is greater than a

You need ot omit the else part, because if b is not greater than a, you need still a comparison with c.

The other two points are:

1. No need to declare a blockwise max, because the outer does not get the value from the condition.

2. You never use the result of the call of getMax.

const getMax = (a, b, c) => {
    let max = a;

    if (b > max) max = b;
    if (c > max) max = c;

    return max;
}



console.log(`max value: ${getMax(2, 72, 189)}`);

There are a few things wrong with your code as pointed out in the comments so the question isn't 100% clear so I present you with the below approach...

function getMax() {
  const nums = arguments;
  var max = null;

  for (let i = 0; i < nums.length; i++) {
    const num = nums[i];
    if (max === null || num > max) {
      max = num;
    }
  }

  return max;
}

This function accepts an infinite number of arguments to compare against and does not restrict to a fix number of inputs. For example, the below are all valid uses:

const validExample1 = getMax(33, 72, 189, 4, 1); // Output: 189
const validExample2 = getMax(2, 2); // Output: 2
const validExample3 = getMax(320, 1, 8); // Output: 320
const validExample4 = getMax(-1, -200, -34); // Output: -1

By not using the arrow function expression you can use the arguments keyword to retrieve an iterable object of all values. Alternatively, if requirements are to use arrow functions you can simply use the spread syntax (...) do...

const getMax = ( ...nums ) => {
  var max = null;

  for (let i = 0; i < nums.length; i++) {
    const num = nums[i];
    if (max === null || num > max) {
      max = num;
    }
  }

  return max;
}

A full working example:

const number1 = 3;
const number2 = 72;
const number3 = 189;

function getMax() {

  const nums = arguments;
  var max = null;

  for (let i = 0; i < nums.length; i++) {
    const num = nums[i];
    if (max === null || num > max) {
      max = num;
    }
  }

  return max;
}

const result = getMax(number1, number2, number3);

console.log(`Nilai maksimum adalah ${result}`);