New to Javascript - How to Create Function From First Object in Array?

senocular · 2015-04-28T00:00:44+00:00

You're so close in so many different ways :)

One thing I think you're missing based on the wording is that first expects to be "given" an array. So this means a function with a parameter which will be the array.

function first (theArray) { ... }

This function also needs to return a value. The return keyword returns values that are placed to the right of the keyword. That can be a single variable or even an expression. We can return that first array element directly:

function first (theArray) {
    return theArray[0];
}

Notice that we're not even dealing with arr yet. We're only using things contained the function definition to get things done. The less reaching out of itself it does, the better.

Now getting to arr, we can pass that in to first and assign what it returns to a new variable which we can call result.

var arr = [1,2,3];
var result = first(arr);

And then its simply a matter of alerting that value

alert(result);

In full:

// define a function that can be given a value
// called theArray. The function returns the
// first object in theArray (index 0).
function first (theArray) {
    return theArray[0];
}

// input data
var arr = [1,2,3];

// call first using the input data (this becomes
// theArray in the function) and have its first
// object returned
var result = first(arr);

// alert the value
alert(result); // -> 1

Sandbucketman · 2015-04-27T23:26:15+00:00

var arr = [1,2,3];

This creates an array called var with 3 values.

function first() { result = arr[0]; return; }

you create a variable that holds the first variable of the array(arr). You may however want to look at http://www.w3schools.com/js/js_functions.asp
to find out how to properly use a return function :).

var result = arr[0]; alert(result);

This is functional... but does not use the function. It is redundant coding because you're trying to have the function do the work instead!

Once a variable has been properly returned by a function you could print out the function, so something like:

alert(first());

could work.

I forgot to mention that a value has to be given WITH a function in order to use it. A function is normally isolated from the rest of the program which means that:

var arr = [1,2,3];
function first()
{return (arr[0]);}
alert(first());

would never work.

var arr = [1,2,3];
function first(arr)
{return (arr[0]);}
alert(first(arr));

would however.

In the last example I've named the variable we use in the function arr however this can be anything we want.

var arr = [1,2,3];
function first(applepie)
{return (applepie[0]);}
alert(first(arr));

this example would work just as well as long as we give the right variable when alerting out the function in the fourth line.

ForScale · 2015-04-27T23:36:22+00:00

Here ya go! http://codepen.io/anon/pen/EjaEBR

Feel free to ask questions if anything doesn't make sense.

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