How to write information into array inside of function? (Javascript)

Question

I've got a problem. I have a function (It doesn't return any information) and array. I need to write information into array inside of function that is inside of another function.

It should be look like this example, but in javascript:

#include <stdio.h>

void setDefault(int * array);
void setDefault2(int * array2);


int main(void)
{
    int a[]={0,1,2};
    setDefault(a);
    printf("%d\n",a[0]);
    return 0;
}

void setDefault(int * array)
{
    setDefault2(array);
}

void setDefault2(int * array2)
{
    array2[0]=-1;
}

PS. Thanks for help

What have you tried so far? Hint: Arrays are already passed as a reference in JavaScript, so just forget the pointers in the C code and it should be straightforward to convert it to JavaScript. — casablanca
– casablanca, Commented Dec 13, 2010 at 4:55

Juho Vepsäläinen · Accepted Answer · 2010-12-13 04:56:18Z

1

I think something like this ought to do the trick:

var myArray = [0, 1, 2];

function setDefault(ar) {
    setDefault2(ar);
}

function setDefault2(ar) {
    // do the thingy you want here
    ar[0]--;
}

// test
setDefault(myArray);
// myArray should contain [-1, 1, 2] now

answered Dec 13, 2010 at 4:56

Juho Vepsäläinen

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5 Comments

casablanca Over a year ago

That's some dangerous use of for ... in over there. And by the way, the OP only wanted array[0] = -1.

Juho Vepsäläinen Over a year ago

Yeah. I just changed that. :)

Rusfearuth Over a year ago

Thank you, but it didn't help =(

Jamie Wong Over a year ago

You're assuming that the input array will always have 0 as the first element.

Rusfearuth Over a year ago

Yep. It's always first element of array.

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