return和console.log（）有什么区别

Question

I get different outputs when I use console.log() in my function vs when I use the return statement.

When I run the function with the return statement I get a one word output which is one of the following: 'fizz' 'buzz' or 'fizzbuzz', but when I run the function using console.log the output is counting to the limit and saying 'fizz' 'buzz' or 'fizzbuzz' whenever it comes across a multiple of 3, 5 or both/ why is this so?

input = fizzBuzz(100)
console.log(input)

function fizzBuzz(limit){
    for (let i = 0; i <= limit; ++i)
    if (i % 3 === 0 && i % 5 === 0) 
    console.log('fizzbuzz')
    else if (i % 3 === 0)
    console.log('fizz')
    else if (i % 5 === 0)
    console.log('buzz')
    else console.log(i)
}


input = fizzBuzz(100)
console.log(input)

function fizzBuzz(limit){
    for (let i = 0; i <= limit; ++i) {
        if (i % 3 === 0 && i % 5 === 0)
            return 'fizzbuzz'
        else if (i % 3 === 0)
            return 'fizz'
        else if (i % 5 === 0)
            return 'buzz'
        else return i
    }
}

I think it is because the return statement stops the function from executing anything further but I am not sure, still new and self teaching!

Answer 1

You are correct in stating that it is because the return statement exits the function.

This is also the case in python,java, and many other languages.

Cheers!

Answer 2

Here's what each different function does:

function fizzBuzz(limit) {
    for (let i = 0; i <= limit; ++i)
        if (i % 3 === 0 && i % 5 === 0)
            console.log('fizzbuzz')
        else if (i % 3 === 0)
            console.log('fizz')
        else if (i % 5 === 0)
            console.log('buzz')
        else console.log(i)
}

This iterates through to limit , and console.log s the FizzBuzz test result each time.

function fizzBuzz(limit){
    for (let i = 0; i <= limit; ++i) {
        if (i % 3 === 0 && i % 5 === 0)
            return 'fizzbuzz'
        else if (i % 3 === 0)
            return 'fizz'
        else if (i % 5 === 0)
            return 'buzz'
        else return i
    }
}

This iterates through to limit , and returns a single value from the function - the result of the FizzBuzz test on the first iteration.

So essentially, one function logs all the FizzBuzz results to the console, and the other returns one FizzBuzz result, which you are logging to the console manually.

Answer 3

return evaluates its argument (if supplied) and ends the execution of the containing function immediately.

console.log evaluates its argument and prints it, continuing the execution of the function it's called from.

So in your example with return , the fact that you're in a for-loop that goes limit times doesn't matter, because you'll only go through it once and return from fizzBuzz .

Putting it all together with another example:

function print_dog() {
  console.log('dog');
  return;
  console.log('cat');
}

If you then call print_dog() , you'll see the output dog , but you won't see the output cat , because return ends execution of print_dog before it can get to console.log('cat');

Answer 4

Yes, you are thinking on the correct lines.

A return statement in a function will return a value and stop further execution. Where as Console.log() is a side effect producing function that will print the arguments supplied to it in the console.

Having a console.log() inside a function is like calling a function within a function.