node js TypeError: callBack is not a function

Question

Here two functions

function pushArray(data, array){
    var index = -1;
    array.forEach(function(item) { 
        if(item.name === data.name) { 
            index = array.indexOf(item);
            console.log('found existing item at ' + index);
        }
    });
    if(index >= 0){
        array[index] = newItem;
    }else {
        array.push(newItem);        
    }
}

function showData(data, array){
    try {
        if(data){
            console.log('data \n');
            console.log(data.toString());
            console.log(array);
        }
    } catch (error) {
        console.log("Showing data caused error: " + error);
    }
}

This is how the callbacks are called

fsReadFile(csvPath1, pushArray. array1);
fsReadFile(csvPath1, showData, array1);

function fsReadFile (filePath, callBack, array) {
    fs.readFile(filePath, function(err, data) {
        if(err) {
            console.error(err);
        }
        callBack(data, array);
    });
}

the show data shows either data and array when send as callback but the pushArray doesn't work as callback as node js complains

    array.forEach(function(item) {
         ^

TypeError: Cannot read property 'forEach' of undefined

Is that more an callback or array issue ? If anyone could explain the root cause ?

Nowhere in this code do you use pushArray (as a callback or otherwise). We have no way of telling why the second argument to it is not an object with a forEach property. — Quentin
– Quentin, Commented Oct 10, 2016 at 13:05
added some calling code. Again the show Data works with that — user3732793
– user3732793, Commented Oct 10, 2016 at 13:10
@user3732793 — The "calling code" still doesn't mention the pushArray function. — Quentin
– Quentin, Commented Oct 10, 2016 at 13:12

Quentin · Accepted Answer · 2016-10-10 13:15:22Z

1

fsReadFile(csvPath1, pushArray(). array1);

You are calling pushArray immediately, with no arguments (so array is undefined), and the return value is passed as the second argument. Don't call it there.

Then you have a typo where you have a . instead of a comma (so you try to read the array1 property of the return value of pushArray() and don't pass a third argument at all).

fsReadFile(csvPath1, pushArray, array1);

answered Oct 10, 2016 at 13:15

Quentin

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1 Comment

user3732793 Over a year ago

oh man ...you are absolutely right there is a typo...notepad is probably not a good editor....

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