Function returns only first value

Question

I realized that when I put a loop inside a function and want to return the value it will give me only first value. Like in this example:

var arr = [[1,2], [3,4], [5,6]];

function getVal(item) {
    var result;
    for (var i = 0; i < item.length; i++) {
        for (var j = 0; j < item[i].length; j++) {
            return (item[i][j])
        }
    }
}

console.log(getVal(arr));

It will give me only the value of 1. But when I put console.log instead of return in function it will give me expected result (1,2,3,4,5,6). What's wrong here?

The function is performing exactly as expected. What are you wanting to happen? This function will always return the value at arr[0][0], which is 1. If you replace the return with a console.log, then it will loop over every possible value. — Dave Goodchild, May 13 '18 at 19:54
I'm just not sure if putting `console.log` inside loop is a good practice? What if I want to get whole result, not only the first element? — muszynov, May 13 '18 at 19:54
Possible duplicate of [Does return stop a loop?](https://stackoverflow.com/questions/11714503/does-return-stop-a-loop) — GalAbra, May 13 '18 at 19:55
@icelandico a console.log inside a loop is fine, but best to use only for debugging. You need to accumulate the values in another array if you want to flatten that array. — Dave Goodchild, May 13 '18 at 19:55
@icelandico people are adding a lot of solutions that will give you the result you appear to be looking for, but I suspect if you're learning Javascript, so go with the solution you understand at this stage, you'll get to the more complex `(inputArr) => [].concat(...inputArr);` solutions later and as well they don't work in all browsers! — Dave Goodchild, May 13 '18 at 19:58

score 2 · Accepted Answer · answered May 13 '18 at 19:53

You could collect the values and return at the end of the function instead of an early exit with one value.

function getVal(item) {
    var result = [];
    for (var i = 0; i < item.length; i++) {
        for (var j = 0; j < item[i].length; j++) {
            result.push(item[i][j]);
        }
    }
    return result;
}

var arr = [[1, 2], [3, 4], [5, 6]];

console.log(getVal(arr));

score 1 · Answer 2 · answered May 13 '18 at 19:53

1

The return keyword will end the function with the given return value. console.log() just gives the output of the value.

answered May 13 '18 at 19:53

Tyr

2,810
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score 1 · Answer 3 · answered May 13 '18 at 19:54

1

this should get u going:

var arr = [[1,2], [3,4], [5,6]];

function getVal(item) {
    var result = [];
    for (var i = 0; i < item.length; i++) {
        for (var j = 0; j < item[i].length; j++) {
            result.push(item[i][j]);
        }
    }
    return result;
}

console.log(getVal(arr));

answered May 13 '18 at 19:54

Ali Yılmaz

1,657
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That's what I wanted. I missed the part of creating an array. Thank You. – muszynov May 13 '18 at 19:55
@icelandico looks like youre missing important conceptual stuff here. I would suggest you to delve deeper into basic concepts like printing, returning so that you become a better developer. Best of luck. – Ali Yılmaz May 13 '18 at 19:56

score 0 · Answer 4 · answered May 13 '18 at 19:55

0

If you want to return a flat mapping of the input, you'll probably be better off avoiding the for loops entirely:

const arr = [[1,2], [3,4], [5,6]];
const getVal = (inputArr) => [].concat(...inputArr);
console.log(getVal(arr));

answered May 13 '18 at 19:55

CertainPerformance

356,069
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this answer is correct, but assumes a lot in terms of the available javascript version and is likely more complicated than the OP can deal with just now. – Dave Goodchild May 13 '18 at 19:59

Function returns only first value

4 Answers4