How to assign a function to a javascript variable

Question

I have a requirement where I need to access an array element using its function.

For example, I have Array A[], now I want to create array B, such that

A[i] === B[i].value()

I tried below code but I am getting error as B[i].value is not a function

<script>
function test(A) {
    var B = new Array();
    for(var i=0; i<A.length; i++) {
        B[i] = function value() {
                return A[i];
            };
    }

    for(var i=0; i< B.length; i++) {
        console.log(B[i].value());
    }
    return B;
}

A=[1,2,3];
B = test(A);
</script>

What is the correct way for this?

The (optional) name of a function expression is only available within the function, it doesn't create a named property of the object it's assigned to. — RobG
– RobG, Commented Mar 21, 2018 at 20:24

Ele · Accepted Answer · 2018-03-21 20:35:52Z

6

You need to assign an object instead:

B[i] = {
    value: function () {
        return A[i];
    }
}

To avoid any problems with the scope of i, you can use the statement let

The let statement declares a block scope local variable, optionally initializing it to a value.

function test(A) {
  var B = new Array();
  for (let i = 0; i < A.length; i++) {
    B[i] = {
      value: function() {
        return A[i];
      }
    };
  }

  for (let k = 0; k < B.length; k++) {
    console.log(B[k].value());
  }
  return B;
}

var B = test([1, 2, 3]);
console.log(B)

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Mar 21, 2018 at 20:35

answered Mar 21, 2018 at 20:21

Ele

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8 Comments

Learner Over a year ago

Thanks Ele, Is there any other way to add this function?

Igor Over a year ago

closures people! Change the second counter to j. Six votes - amusing!

Learner Over a year ago

Yes, If I use` j` in my second loop instead of i, it did not work, got error

Ele Over a year ago

@Igor six votes because the OP wants to call the function as follow B[index].value(). Of course, you're right about the scope problem. See the updated answer!

Igor Over a year ago

@Ele OP also wants B[i].value === B[j].value. OP does not know what they want.

|

Code_Frank · Accepted Answer · 2018-03-21 20:24:13Z

1

You could make value anonymous e.g. B[i] = function () { /* Your code */ } then just call B[i]() instead of B[i].value()

answered Mar 21, 2018 at 20:24

Code_Frank

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